diff --git a/calculations.py b/calculations.py
index a7b3aa9..c16db1e 100644
--- a/calculations.py
+++ b/calculations.py
@@ -3,16 +3,34 @@ Pure calculation functions for DCA transaction processing.
 
 These functions have no external dependencies (no lnbits, no database)
 and can be easily tested in isolation.
+
+All monetary calculations use Decimal for precision. Satoshi amounts
+remain as int since they are the smallest indivisible unit.
 """
 
-from typing import Dict, Tuple
+from decimal import Decimal, ROUND_HALF_UP
+from typing import Dict, Tuple, Union
+
+# Type alias for values that can be Decimal or numeric types that will be converted
+DecimalLike = Union[Decimal, float, int, str]
+
+
+def to_decimal(value: DecimalLike) -> Decimal:
+    """Convert a value to Decimal, handling floats carefully."""
+    if isinstance(value, Decimal):
+        return value
+    # Convert floats via string to avoid binary float precision issues
+    # e.g., Decimal(0.055) gives 0.054999999... but Decimal("0.055") is exact
+    if isinstance(value, float):
+        return Decimal(str(value))
+    return Decimal(value)
 
 
 def calculate_commission(
     crypto_atoms: int,
-    commission_percentage: float,
-    discount: float = 0.0
-) -> Tuple[int, int, float]:
+    commission_percentage: DecimalLike,
+    discount: DecimalLike = Decimal("0")
+) -> Tuple[int, int, Decimal]:
     """
     Calculate commission split from a Lamassu transaction.
 
@@ -34,15 +52,25 @@ def calculate_commission(
         Tuple of (base_amount_sats, commission_amount_sats, effective_commission_rate)
 
     Example:
-        >>> calculate_commission(266800, 0.03, 0.0)
-        (259029, 7771, 0.03)
+        >>> calculate_commission(266800, Decimal("0.03"), Decimal("0"))
+        (259029, 7771, Decimal('0.03'))
     """
-    if commission_percentage > 0:
-        effective_commission = commission_percentage * (100 - discount) / 100
-        base_crypto_atoms = round(crypto_atoms / (1 + effective_commission))
+    # Convert inputs to Decimal for precise calculations
+    comm_pct = to_decimal(commission_percentage)
+    disc = to_decimal(discount)
+
+    if comm_pct > 0:
+        # effective = commission_percentage * (100 - discount) / 100
+        effective_commission = comm_pct * (Decimal("100") - disc) / Decimal("100")
+
+        # base = crypto_atoms / (1 + effective_commission), rounded to nearest int
+        divisor = Decimal("1") + effective_commission
+        exact_base = Decimal(crypto_atoms) / divisor
+        # Use ROUND_HALF_UP (standard rounding: 0.5 rounds up)
+        base_crypto_atoms = int(exact_base.quantize(Decimal("1"), rounding=ROUND_HALF_UP))
         commission_amount_sats = crypto_atoms - base_crypto_atoms
     else:
-        effective_commission = 0.0
+        effective_commission = Decimal("0")
         base_crypto_atoms = crypto_atoms
         commission_amount_sats = 0
 
@@ -51,8 +79,8 @@ def calculate_commission(
 
 def calculate_distribution(
     base_amount_sats: int,
-    client_balances: Dict[str, float],
-    min_balance_threshold: float = 0.01
+    client_balances: Dict[str, DecimalLike],
+    min_balance_threshold: DecimalLike = Decimal("0.01")
 ) -> Dict[str, int]:
     """
     Calculate proportional distribution of sats to clients based on their fiat balances.
@@ -69,15 +97,18 @@ def calculate_distribution(
         Dict of {client_id: allocated_sats}
 
     Example:
-        >>> calculate_distribution(100000, {"a": 500.0, "b": 500.0})
+        >>> calculate_distribution(100000, {"a": Decimal("500"), "b": Decimal("500")})
         {"a": 50000, "b": 50000}
     """
-    # Filter out clients with balance below threshold
-    active_balances = {
-        client_id: balance
-        for client_id, balance in client_balances.items()
-        if balance >= min_balance_threshold
-    }
+    # Convert threshold to Decimal
+    threshold = to_decimal(min_balance_threshold)
+
+    # Filter out clients with balance below threshold, converting to Decimal
+    active_balances: Dict[str, Decimal] = {}
+    for client_id, balance in client_balances.items():
+        bal = to_decimal(balance)
+        if bal >= threshold:
+            active_balances[client_id] = bal
 
     if not active_balances:
         return {}
@@ -90,11 +121,13 @@ def calculate_distribution(
     # First pass: calculate base allocations and track for remainder distribution
     client_calculations = []
     distributed_sats = 0
+    base_sats_decimal = Decimal(base_amount_sats)
 
     for client_id, balance in active_balances.items():
         proportion = balance / total_balance
-        exact_share = base_amount_sats * proportion
-        allocated_sats = round(exact_share)
+        exact_share = base_sats_decimal * proportion
+        # Round to nearest integer using ROUND_HALF_UP
+        allocated_sats = int(exact_share.quantize(Decimal("1"), rounding=ROUND_HALF_UP))
 
         client_calculations.append({
             'client_id': client_id,
@@ -109,8 +142,9 @@ def calculate_distribution(
 
     if remainder != 0:
         # Sort by largest fractional remainder to distribute fairly
+        # The fractional part is exact_share - allocated_sats
         client_calculations.sort(
-            key=lambda x: x['exact_share'] - x['allocated_sats'],
+            key=lambda x: x['exact_share'] - Decimal(x['allocated_sats']),
             reverse=True
         )
 
@@ -131,7 +165,7 @@ def calculate_distribution(
     return distributions
 
 
-def calculate_exchange_rate(base_crypto_atoms: int, fiat_amount: float) -> float:
+def calculate_exchange_rate(base_crypto_atoms: int, fiat_amount: DecimalLike) -> Decimal:
     """
     Calculate exchange rate in sats per fiat unit.
 
@@ -140,8 +174,9 @@ def calculate_exchange_rate(base_crypto_atoms: int, fiat_amount: float) -> float
         fiat_amount: Fiat amount dispensed
 
     Returns:
-        Exchange rate as sats per fiat unit
+        Exchange rate as sats per fiat unit (Decimal for precision)
     """
-    if fiat_amount <= 0:
-        return 0.0
-    return base_crypto_atoms / fiat_amount
+    fiat = to_decimal(fiat_amount)
+    if fiat <= 0:
+        return Decimal("0")
+    return Decimal(base_crypto_atoms) / fiat
diff --git a/crud.py b/crud.py
index 94c1d20..2516f52 100644
--- a/crud.py
+++ b/crud.py
@@ -1,5 +1,6 @@
 # Description: This file contains the CRUD operations for talking to the database.
 
+from decimal import Decimal
 from typing import List, Optional, Union
 from datetime import datetime, timezone
 
@@ -18,16 +19,33 @@ from .models import (
 db = Database("ext_satoshimachine")
 
 
+def prepare_for_db(values: dict) -> dict:
+    """
+    Convert Decimal values to float for SQLite compatibility.
+
+    SQLite doesn't support Decimal natively - it stores DECIMAL as REAL (float).
+    This function converts Decimal values to float before database writes.
+    The Pydantic models handle converting float back to Decimal on read.
+    """
+    result = {}
+    for k, v in values.items():
+        if isinstance(v, Decimal):
+            result[k] = float(v)
+        else:
+            result[k] = v
+    return result
+
+
 # DCA Client CRUD Operations
 async def create_dca_client(data: CreateDcaClientData) -> DcaClient:
     client_id = urlsafe_short_hash()
     await db.execute(
         """
-        INSERT INTO satoshimachine.dca_clients 
+        INSERT INTO satoshimachine.dca_clients
         (id, user_id, wallet_id, username, dca_mode, fixed_mode_daily_limit, status, created_at, updated_at)
         VALUES (:id, :user_id, :wallet_id, :username, :dca_mode, :fixed_mode_daily_limit, :status, :created_at, :updated_at)
         """,
-        {
+        prepare_for_db({
             "id": client_id,
             "user_id": data.user_id,
             "wallet_id": data.wallet_id,
@@ -37,7 +55,7 @@ async def create_dca_client(data: CreateDcaClientData) -> DcaClient:
             "status": "active",
             "created_at": datetime.now(),
             "updated_at": datetime.now()
-        }
+        })
     )
     return await get_dca_client(client_id)
 
@@ -69,14 +87,14 @@ async def update_dca_client(client_id: str, data: UpdateDcaClientData) -> Option
     update_data = {k: v for k, v in data.dict().items() if v is not None}
     if not update_data:
         return await get_dca_client(client_id)
-    
+
     update_data["updated_at"] = datetime.now()
     set_clause = ", ".join([f"{k} = :{k}" for k in update_data.keys()])
     update_data["id"] = client_id
-    
+
     await db.execute(
         f"UPDATE satoshimachine.dca_clients SET {set_clause} WHERE id = :id",
-        update_data
+        prepare_for_db(update_data)
     )
     return await get_dca_client(client_id)
 
@@ -93,11 +111,11 @@ async def create_deposit(data: CreateDepositData) -> DcaDeposit:
     deposit_id = urlsafe_short_hash()
     await db.execute(
         """
-        INSERT INTO satoshimachine.dca_deposits 
+        INSERT INTO satoshimachine.dca_deposits
         (id, client_id, amount, currency, status, notes, created_at)
         VALUES (:id, :client_id, :amount, :currency, :status, :notes, :created_at)
         """,
-        {
+        prepare_for_db({
             "id": deposit_id,
             "client_id": data.client_id,
             "amount": data.amount,
@@ -105,7 +123,7 @@ async def create_deposit(data: CreateDepositData) -> DcaDeposit:
             "status": "pending",
             "notes": data.notes,
             "created_at": datetime.now()
-        }
+        })
     )
     return await get_deposit(deposit_id)
 
@@ -158,13 +176,13 @@ async def create_dca_payment(data: CreateDcaPaymentData) -> DcaPayment:
     payment_id = urlsafe_short_hash()
     await db.execute(
         """
-        INSERT INTO satoshimachine.dca_payments 
-        (id, client_id, amount_sats, amount_fiat, exchange_rate, transaction_type, 
+        INSERT INTO satoshimachine.dca_payments
+        (id, client_id, amount_sats, amount_fiat, exchange_rate, transaction_type,
          lamassu_transaction_id, payment_hash, status, created_at, transaction_time)
         VALUES (:id, :client_id, :amount_sats, :amount_fiat, :exchange_rate, :transaction_type,
                 :lamassu_transaction_id, :payment_hash, :status, :created_at, :transaction_time)
         """,
-        {
+        prepare_for_db({
             "id": payment_id,
             "client_id": data.client_id,
             "amount_sats": data.amount_sats,
@@ -176,7 +194,7 @@ async def create_dca_payment(data: CreateDcaPaymentData) -> DcaPayment:
             "status": "pending",
             "created_at": datetime.now(),
             "transaction_time": data.transaction_time
-        }
+        })
     )
     return await get_dca_payment(payment_id)
 
@@ -295,22 +313,22 @@ async def get_fixed_mode_clients() -> List[DcaClient]:
 # Lamassu Configuration CRUD Operations
 async def create_lamassu_config(data: CreateLamassuConfigData) -> LamassuConfig:
     config_id = urlsafe_short_hash()
-    
+
     # Deactivate any existing configs first (only one active config allowed)
     await db.execute(
         "UPDATE satoshimachine.lamassu_config SET is_active = false, updated_at = :updated_at",
         {"updated_at": datetime.now()}
     )
-    
+
     await db.execute(
         """
-        INSERT INTO satoshimachine.lamassu_config 
+        INSERT INTO satoshimachine.lamassu_config
         (id, host, port, database_name, username, password, source_wallet_id, commission_wallet_id, is_active, created_at, updated_at,
          use_ssh_tunnel, ssh_host, ssh_port, ssh_username, ssh_password, ssh_private_key, max_daily_limit_gtq)
         VALUES (:id, :host, :port, :database_name, :username, :password, :source_wallet_id, :commission_wallet_id, :is_active, :created_at, :updated_at,
                 :use_ssh_tunnel, :ssh_host, :ssh_port, :ssh_username, :ssh_password, :ssh_private_key, :max_daily_limit_gtq)
         """,
-        {
+        prepare_for_db({
             "id": config_id,
             "host": data.host,
             "port": data.port,
@@ -329,7 +347,7 @@ async def create_lamassu_config(data: CreateLamassuConfigData) -> LamassuConfig:
             "ssh_password": data.ssh_password,
             "ssh_private_key": data.ssh_private_key,
             "max_daily_limit_gtq": data.max_daily_limit_gtq
-        }
+        })
     )
     return await get_lamassu_config(config_id)
 
@@ -360,14 +378,14 @@ async def update_lamassu_config(config_id: str, data: UpdateLamassuConfigData) -
     update_data = {k: v for k, v in data.dict().items() if v is not None}
     if not update_data:
         return await get_lamassu_config(config_id)
-    
+
     update_data["updated_at"] = datetime.now()
     set_clause = ", ".join([f"{k} = :{k}" for k in update_data.keys()])
     update_data["id"] = config_id
-    
+
     await db.execute(
         f"UPDATE satoshimachine.lamassu_config SET {set_clause} WHERE id = :id",
-        update_data
+        prepare_for_db(update_data)
     )
     return await get_lamassu_config(config_id)
 
@@ -436,9 +454,9 @@ async def create_lamassu_transaction(data: CreateLamassuTransactionData) -> Stor
     transaction_id = urlsafe_short_hash()
     await db.execute(
         """
-        INSERT INTO satoshimachine.lamassu_transactions 
-        (id, lamassu_transaction_id, fiat_amount, crypto_amount, commission_percentage, 
-         discount, effective_commission, commission_amount_sats, base_amount_sats, 
+        INSERT INTO satoshimachine.lamassu_transactions
+        (id, lamassu_transaction_id, fiat_amount, crypto_amount, commission_percentage,
+         discount, effective_commission, commission_amount_sats, base_amount_sats,
          exchange_rate, crypto_code, fiat_code, device_id, transaction_time, processed_at,
          clients_count, distributions_total_sats)
         VALUES (:id, :lamassu_transaction_id, :fiat_amount, :crypto_amount, :commission_percentage,
@@ -446,7 +464,7 @@ async def create_lamassu_transaction(data: CreateLamassuTransactionData) -> Stor
                 :exchange_rate, :crypto_code, :fiat_code, :device_id, :transaction_time, :processed_at,
                 :clients_count, :distributions_total_sats)
         """,
-        {
+        prepare_for_db({
             "id": transaction_id,
             "lamassu_transaction_id": data.lamassu_transaction_id,
             "fiat_amount": data.fiat_amount,
@@ -464,7 +482,7 @@ async def create_lamassu_transaction(data: CreateLamassuTransactionData) -> Stor
             "processed_at": datetime.now(),
             "clients_count": 0,  # Will be updated after distributions
             "distributions_total_sats": 0  # Will be updated after distributions
-        }
+        })
     )
     return await get_lamassu_transaction(transaction_id)
 
diff --git a/models.py b/models.py
index e4bf64d..3e6aa2a 100644
--- a/models.py
+++ b/models.py
@@ -1,18 +1,29 @@
 # Description: Pydantic data models dictate what is passed between frontend and backend.
 
 from datetime import datetime
+from decimal import Decimal
 from typing import Optional
 
 from pydantic import BaseModel, validator
 
 
+def _to_decimal(v):
+    """Convert a value to Decimal, handling floats from database."""
+    if v is None:
+        return None
+    if isinstance(v, Decimal):
+        return v
+    # Convert via string to avoid float precision issues
+    return Decimal(str(v))
+
+
 # DCA Client Models
 class CreateDcaClientData(BaseModel):
     user_id: str
     wallet_id: str
     username: str
     dca_mode: str = "flow"  # 'flow' or 'fixed'
-    fixed_mode_daily_limit: Optional[float] = None
+    fixed_mode_daily_limit: Optional[Decimal] = None
 
 
 class DcaClient(BaseModel):
@@ -21,44 +32,60 @@ class DcaClient(BaseModel):
     wallet_id: str
     username: Optional[str]
     dca_mode: str
-    fixed_mode_daily_limit: Optional[int]
+    fixed_mode_daily_limit: Optional[Decimal]
     status: str
     created_at: datetime
     updated_at: datetime
 
+    @validator('fixed_mode_daily_limit', pre=True)
+    def convert_fixed_mode_daily_limit(cls, v):
+        return _to_decimal(v)
+
+    class Config:
+        json_encoders = {Decimal: lambda v: float(v)}
+
 
 class UpdateDcaClientData(BaseModel):
     username: Optional[str] = None
     dca_mode: Optional[str] = None
-    fixed_mode_daily_limit: Optional[float] = None
+    fixed_mode_daily_limit: Optional[Decimal] = None
     status: Optional[str] = None
 
 
 # Deposit Models (Now storing GTQ directly)
 class CreateDepositData(BaseModel):
     client_id: str
-    amount: float  # Amount in GTQ (e.g., 150.75)
+    amount: Decimal  # Amount in GTQ (e.g., 150.75)
     currency: str = "GTQ"
     notes: Optional[str] = None
-    
-    @validator('amount')
+
+    @validator('amount', pre=True)
     def round_amount_to_cents(cls, v):
         """Ensure amount is rounded to 2 decimal places for DECIMAL(10,2) storage"""
         if v is not None:
-            return round(float(v), 2)
+            # Convert to Decimal via string to avoid float precision issues
+            d = Decimal(str(v)) if not isinstance(v, Decimal) else v
+            return d.quantize(Decimal("0.01"))
         return v
 
 
 class DcaDeposit(BaseModel):
     id: str
     client_id: str
-    amount: float  # Amount in GTQ (e.g., 150.75)
+    amount: Decimal  # Amount in GTQ (e.g., 150.75)
     currency: str
     status: str  # 'pending' or 'confirmed'
     notes: Optional[str]
     created_at: datetime
     confirmed_at: Optional[datetime]
 
+    @validator('amount', pre=True)
+    def convert_amount(cls, v):
+        return _to_decimal(v)
+
+    class Config:
+        json_encoders = {Decimal: lambda v: float(v)}
+
 
 class UpdateDepositStatusData(BaseModel):
     status: str
@@ -69,8 +96,8 @@ class UpdateDepositStatusData(BaseModel):
 class CreateDcaPaymentData(BaseModel):
     client_id: str
     amount_sats: int
-    amount_fiat: float  # Amount in GTQ (e.g., 150.75)
-    exchange_rate: float
+    amount_fiat: Decimal  # Amount in GTQ (e.g., 150.75)
+    exchange_rate: Decimal
     transaction_type: str  # 'flow', 'fixed', 'manual', 'commission'
     lamassu_transaction_id: Optional[str] = None
     payment_hash: Optional[str] = None
@@ -81,8 +108,8 @@ class DcaPayment(BaseModel):
     id: str
     client_id: str
     amount_sats: int
-    amount_fiat: float  # Amount in GTQ (e.g., 150.75)
-    exchange_rate: float
+    amount_fiat: Decimal  # Amount in GTQ (e.g., 150.75)
+    exchange_rate: Decimal
     transaction_type: str
     lamassu_transaction_id: Optional[str]
     payment_hash: Optional[str]
@@ -90,38 +117,55 @@ class DcaPayment(BaseModel):
     created_at: datetime
     transaction_time: Optional[datetime] = None  # Original ATM transaction time
 
+    @validator('amount_fiat', 'exchange_rate', pre=True)
+    def convert_decimals(cls, v):
+        return _to_decimal(v)
+
+    class Config:
+        json_encoders = {Decimal: lambda v: float(v)}
+
 
 # Client Balance Summary (Now storing GTQ directly)
 class ClientBalanceSummary(BaseModel):
     client_id: str
-    total_deposits: float  # Total confirmed deposits in GTQ
-    total_payments: float  # Total payments made in GTQ
-    remaining_balance: float  # Available balance for DCA in GTQ
+    total_deposits: Decimal  # Total confirmed deposits in GTQ
+    total_payments: Decimal  # Total payments made in GTQ
+    remaining_balance: Decimal  # Available balance for DCA in GTQ
     currency: str
 
+    @validator('total_deposits', 'total_payments', 'remaining_balance', pre=True)
+    def convert_decimals(cls, v):
+        return _to_decimal(v)
+
+    class Config:
+        json_encoders = {Decimal: lambda v: float(v)}
+
 
 # Transaction Processing Models
 class LamassuTransaction(BaseModel):
     transaction_id: str
-    amount_fiat: float  # Amount in GTQ (e.g., 150.75)
+    amount_fiat: Decimal  # Amount in GTQ (e.g., 150.75)
     amount_crypto: int
-    exchange_rate: float
+    exchange_rate: Decimal
     transaction_type: str  # 'cash_in' or 'cash_out'
     status: str
     timestamp: datetime
 
+    class Config:
+        json_encoders = {Decimal: lambda v: float(v)}
+
 
 # Lamassu Transaction Storage Models
 class CreateLamassuTransactionData(BaseModel):
     lamassu_transaction_id: str
-    fiat_amount: float  # Amount in GTQ (e.g., 150.75)
+    fiat_amount: Decimal  # Amount in GTQ (e.g., 150.75)
     crypto_amount: int
-    commission_percentage: float
-    discount: float = 0.0
-    effective_commission: float
+    commission_percentage: Decimal
+    discount: Decimal = Decimal("0")
+    effective_commission: Decimal
     commission_amount_sats: int
     base_amount_sats: int
-    exchange_rate: float
+    exchange_rate: Decimal
     crypto_code: str = "BTC"
     fiat_code: str = "GTQ"
     device_id: Optional[str] = None
@@ -131,14 +175,14 @@ class CreateLamassuTransactionData(BaseModel):
 class StoredLamassuTransaction(BaseModel):
     id: str
     lamassu_transaction_id: str
-    fiat_amount: float  # Amount in GTQ (e.g., 150.75)
+    fiat_amount: Decimal  # Amount in GTQ (e.g., 150.75)
     crypto_amount: int
-    commission_percentage: float
-    discount: float
-    effective_commission: float
+    commission_percentage: Decimal
+    discount: Decimal
+    effective_commission: Decimal
     commission_amount_sats: int
     base_amount_sats: int
-    exchange_rate: float
+    exchange_rate: Decimal
     crypto_code: str
     fiat_code: str
     device_id: Optional[str]
@@ -147,6 +191,16 @@ class StoredLamassuTransaction(BaseModel):
     clients_count: int  # Number of clients who received distributions
     distributions_total_sats: int  # Total sats distributed to clients
 
+    @validator(
+        'fiat_amount', 'commission_percentage', 'discount',
+        'effective_commission', 'exchange_rate', pre=True
+    )
+    def convert_decimals(cls, v):
+        return _to_decimal(v)
+
+    class Config:
+        json_encoders = {Decimal: lambda v: float(v)}
+
 
 # Lamassu Configuration Models
 class CreateLamassuConfigData(BaseModel):
@@ -167,13 +221,14 @@ class CreateLamassuConfigData(BaseModel):
     ssh_password: Optional[str] = None
     ssh_private_key: Optional[str] = None  # Path to private key file or key content
     # DCA Client Limits
-    max_daily_limit_gtq: float = 2000.0  # Maximum daily limit for Fixed mode clients
-    
-    @validator('max_daily_limit_gtq')
+    max_daily_limit_gtq: Decimal = Decimal("2000")  # Maximum daily limit for Fixed mode clients
+
+    @validator('max_daily_limit_gtq', pre=True)
     def round_max_daily_limit(cls, v):
         """Ensure max daily limit is rounded to 2 decimal places"""
         if v is not None:
-            return round(float(v), 2)
+            d = Decimal(str(v)) if not isinstance(v, Decimal) else v
+            return d.quantize(Decimal("0.01"))
         return v
 
 
@@ -204,7 +259,14 @@ class LamassuConfig(BaseModel):
     last_poll_time: Optional[datetime] = None
     last_successful_poll: Optional[datetime] = None
     # DCA Client Limits
-    max_daily_limit_gtq: float = 2000.0  # Maximum daily limit for Fixed mode clients
+    max_daily_limit_gtq: Decimal = Decimal("2000")  # Maximum daily limit for Fixed mode clients
+
+    @validator('max_daily_limit_gtq', pre=True)
+    def convert_max_daily_limit(cls, v):
+        return _to_decimal(v)
+
+    class Config:
+        json_encoders = {Decimal: lambda v: float(v)}
 
 
 class UpdateLamassuConfigData(BaseModel):
@@ -226,6 +288,6 @@ class UpdateLamassuConfigData(BaseModel):
     ssh_password: Optional[str] = None
     ssh_private_key: Optional[str] = None
     # DCA Client Limits
-    max_daily_limit_gtq: Optional[int] = None
+    max_daily_limit_gtq: Optional[Decimal] = None
 
 
diff --git a/tests/test_calculations.py b/tests/test_calculations.py
index 04262a0..b175421 100644
--- a/tests/test_calculations.py
+++ b/tests/test_calculations.py
@@ -10,7 +10,7 @@ from decimal import Decimal
 from typing import Dict, List, Tuple
 
 # Import from the parent package (following lnurlp pattern)
-from ..calculations import calculate_commission, calculate_distribution, calculate_exchange_rate
+from ..calculations import calculate_commission, calculate_distribution, calculate_exchange_rate, to_decimal
 
 
 # =============================================================================
@@ -245,11 +245,12 @@ class TestDistributionCalculation:
 
             # Convert each client's sats back to fiat
             total_fiat_distributed = sum(
-                sats / exchange_rate for sats in distributions.values()
+                Decimal(sats) / exchange_rate for sats in distributions.values()
             )
 
             # Should equal original fiat amount (within small rounding tolerance)
-            assert abs(total_fiat_distributed - fiat_amount) < 0.01, \
+            fiat_decimal = to_decimal(fiat_amount)
+            assert abs(total_fiat_distributed - fiat_decimal) < Decimal("0.01"), \
                 f"Fiat round-trip failed: {total_fiat_distributed:.2f} != {fiat_amount:.2f} " \
                 f"(crypto={crypto_atoms}, comm={comm_pct}, discount={discount})"
 
@@ -287,11 +288,12 @@ class TestEmpiricalTransactions:
             "expected_base_sats": 259029,
             "expected_commission_sats": 7771,
             "expected_distributions": {
-                # 259029 / 2 = 129514.5 → both get 129514 or 129515
-                # With banker's rounding: 129514.5 → 129514 (even)
-                # Remainder of 1 sat goes to first client by fractional sort
-                "client_a": 129515,
-                "client_b": 129514,
+                # 259029 / 2 = 129514.5 → both round to 129515 (ROUND_HALF_UP)
+                # Total = 259030, remainder = -1
+                # Both have same fractional (-0.5), client_a is first alphabetically
+                # So client_a gets -1 adjustment
+                "client_a": 129514,
+                "client_b": 129515,
             },
         },
         # Add more scenarios from your real data!
diff --git a/tests/test_integration.py b/tests/test_integration.py
new file mode 100644
index 0000000..fc1ff62
--- /dev/null
+++ b/tests/test_integration.py
@@ -0,0 +1,828 @@
+"""
+Integration tests for the full transaction processing flow.
+
+These tests verify that data flows correctly from:
+  CSV parsing → Decimal conversion → calculations → model creation → CRUD
+
+This gives us confidence that real Lamassu transactions will be
+processed correctly end-to-end.
+"""
+
+import pytest
+from decimal import Decimal
+from datetime import datetime, timezone
+from unittest.mock import AsyncMock, MagicMock, patch
+from typing import Dict, Any
+import csv
+import io
+
+from ..calculations import calculate_commission, calculate_distribution, calculate_exchange_rate
+from ..models import (
+    CreateDcaPaymentData,
+    CreateLamassuTransactionData,
+    ClientBalanceSummary,
+    CreateDepositData,
+    DcaDeposit,
+    DcaPayment,
+    StoredLamassuTransaction,
+)
+
+
+# =============================================================================
+# TEST DATA: Real Lamassu CSV output format
+# =============================================================================
+
+# This simulates what execute_ssh_query receives from the database
+LAMASSU_CSV_DATA = {
+    "8.75pct_large": """transaction_id,fiat_amount,crypto_amount,transaction_time,device_id,status,commission_percentage,discount,crypto_code,fiat_code
+abc123,2000,309200,2025-01-10 14:30:00+00,device1,confirmed,0.0875,0,BTC,GTQ""",
+
+    "5.5pct_no_discount": """transaction_id,fiat_amount,crypto_amount,transaction_time,device_id,status,commission_percentage,discount,crypto_code,fiat_code
+def456,2000,309500,2025-01-10 15:00:00+00,device1,confirmed,0.055,0,BTC,GTQ""",
+
+    "5.5pct_90pct_discount": """transaction_id,fiat_amount,crypto_amount,transaction_time,device_id,status,commission_percentage,discount,crypto_code,fiat_code
+ghi789,800,115000,2025-01-10 16:00:00+00,device1,confirmed,0.055,90,BTC,GTQ""",
+
+    "5.5pct_1300gtq_4clients": """transaction_id,fiat_amount,crypto_amount,transaction_time,device_id,status,commission_percentage,discount,crypto_code,fiat_code
+jkl012,1300,205600,2025-01-10 17:00:00+00,device1,confirmed,0.055,0,BTC,GTQ""",
+}
+
+
+def parse_csv_like_transaction_processor(csv_data: str) -> Dict[str, Any]:
+    """
+    Parse CSV data exactly like transaction_processor.execute_ssh_query does.
+
+    This is a copy of the parsing logic to test it in isolation.
+    """
+    reader = csv.DictReader(io.StringIO(csv_data))
+    results = []
+    for row in reader:
+        processed_row = {}
+        for key, value in row.items():
+            if value == '' or value is None:
+                if key == 'crypto_amount':
+                    processed_row[key] = 0
+                elif key == 'fiat_amount':
+                    processed_row[key] = Decimal("0")
+                elif key in ['commission_percentage', 'discount']:
+                    processed_row[key] = Decimal("0")
+                else:
+                    processed_row[key] = None
+            elif key in ['transaction_id', 'device_id', 'crypto_code', 'fiat_code', 'status']:
+                processed_row[key] = str(value)
+            elif key == 'crypto_amount':
+                try:
+                    processed_row[key] = int(float(value))
+                except (ValueError, TypeError):
+                    processed_row[key] = 0
+            elif key == 'fiat_amount':
+                try:
+                    processed_row[key] = Decimal(str(value))
+                except (ValueError, TypeError):
+                    processed_row[key] = Decimal("0")
+            elif key in ['commission_percentage', 'discount']:
+                try:
+                    processed_row[key] = Decimal(str(value))
+                except (ValueError, TypeError):
+                    processed_row[key] = Decimal("0")
+            elif key == 'transaction_time':
+                timestamp_str = value
+                if timestamp_str.endswith('+00'):
+                    timestamp_str = timestamp_str + ':00'
+                elif timestamp_str.endswith('Z'):
+                    timestamp_str = timestamp_str.replace('Z', '+00:00')
+                try:
+                    dt = datetime.fromisoformat(timestamp_str)
+                except ValueError:
+                    dt = datetime.now(timezone.utc)
+                if dt.tzinfo is None:
+                    dt = dt.replace(tzinfo=timezone.utc)
+                elif dt.tzinfo != timezone.utc:
+                    dt = dt.astimezone(timezone.utc)
+                processed_row[key] = dt
+            else:
+                processed_row[key] = value
+        results.append(processed_row)
+    return results[0] if results else {}
+
+
+# =============================================================================
+# CSV PARSING TESTS
+# =============================================================================
+
+class TestCsvParsing:
+    """Test that CSV parsing produces correct Decimal types."""
+
+    def test_parse_8_75pct_transaction(self):
+        """Parse 8.75% commission transaction."""
+        tx = parse_csv_like_transaction_processor(LAMASSU_CSV_DATA["8.75pct_large"])
+
+        assert tx["transaction_id"] == "abc123"
+        assert tx["crypto_amount"] == 309200
+        assert tx["fiat_amount"] == Decimal("2000")
+        assert tx["commission_percentage"] == Decimal("0.0875")
+        assert tx["discount"] == Decimal("0")
+        assert isinstance(tx["fiat_amount"], Decimal)
+        assert isinstance(tx["commission_percentage"], Decimal)
+        assert isinstance(tx["discount"], Decimal)
+
+    def test_parse_5_5pct_with_discount(self):
+        """Parse 5.5% commission with 90% discount."""
+        tx = parse_csv_like_transaction_processor(LAMASSU_CSV_DATA["5.5pct_90pct_discount"])
+
+        assert tx["crypto_amount"] == 115000
+        assert tx["fiat_amount"] == Decimal("800")
+        assert tx["commission_percentage"] == Decimal("0.055")
+        assert tx["discount"] == Decimal("90")
+
+    def test_timestamp_parsing(self):
+        """Verify timestamp is parsed to UTC datetime."""
+        tx = parse_csv_like_transaction_processor(LAMASSU_CSV_DATA["8.75pct_large"])
+
+        assert isinstance(tx["transaction_time"], datetime)
+        assert tx["transaction_time"].tzinfo == timezone.utc
+
+
+# =============================================================================
+# END-TO-END CALCULATION TESTS
+# =============================================================================
+
+class TestEndToEndCalculations:
+    """
+    Test the full flow: CSV → Decimal → calculations → expected results.
+
+    These use the same empirical data as test_calculations.py but verify
+    the data flows correctly through parsing.
+    """
+
+    @pytest.mark.parametrize("csv_key,expected_base,expected_commission", [
+        ("8.75pct_large", 284322, 24878),
+        ("5.5pct_no_discount", 293365, 16135),
+        ("5.5pct_90pct_discount", 114371, 629),
+        ("5.5pct_1300gtq_4clients", 194882, 10718),
+    ])
+    def test_csv_to_commission_calculation(self, csv_key, expected_base, expected_commission):
+        """Verify CSV parsing → commission calculation produces expected results."""
+        # Parse CSV like transaction_processor does
+        tx = parse_csv_like_transaction_processor(LAMASSU_CSV_DATA[csv_key])
+
+        # Calculate commission using parsed Decimal values
+        base, commission, effective = calculate_commission(
+            tx["crypto_amount"],
+            tx["commission_percentage"],
+            tx["discount"]
+        )
+
+        assert base == expected_base, f"Base mismatch for {csv_key}"
+        assert commission == expected_commission, f"Commission mismatch for {csv_key}"
+        assert base + commission == tx["crypto_amount"], "Invariant: base + commission = total"
+
+    def test_full_distribution_flow_two_equal_clients(self):
+        """Test full flow with two equal-balance clients."""
+        tx = parse_csv_like_transaction_processor(LAMASSU_CSV_DATA["8.75pct_large"])
+
+        # Calculate commission
+        base_sats, commission_sats, effective = calculate_commission(
+            tx["crypto_amount"],
+            tx["commission_percentage"],
+            tx["discount"]
+        )
+
+        # Simulate client balances (as would come from database)
+        client_balances = {
+            "client_a": Decimal("1000.00"),
+            "client_b": Decimal("1000.00"),
+        }
+
+        # Calculate distribution
+        distributions = calculate_distribution(base_sats, client_balances)
+
+        # Verify results
+        assert sum(distributions.values()) == base_sats
+        assert len(distributions) == 2
+        # With equal balances, should be roughly equal (±1 sat for rounding)
+        assert abs(distributions["client_a"] - distributions["client_b"]) <= 1
+
+    def test_full_distribution_flow_four_clients(self):
+        """Test the 1300 GTQ transaction with 4 clients of varying balances."""
+        tx = parse_csv_like_transaction_processor(LAMASSU_CSV_DATA["5.5pct_1300gtq_4clients"])
+
+        # Calculate commission
+        base_sats, commission_sats, effective = calculate_commission(
+            tx["crypto_amount"],
+            tx["commission_percentage"],
+            tx["discount"]
+        )
+
+        assert base_sats == 194882
+        assert commission_sats == 10718
+
+        # Use the actual balance proportions from the real scenario
+        client_balances = {
+            "client_a": Decimal("1"),
+            "client_b": Decimal("986"),
+            "client_c": Decimal("14"),
+            "client_d": Decimal("4"),
+        }
+
+        distributions = calculate_distribution(base_sats, client_balances)
+
+        # Verify invariant
+        assert sum(distributions.values()) == base_sats
+
+        # Verify proportions are reasonable
+        total_balance = sum(client_balances.values())
+        for client_id, sats in distributions.items():
+            expected_proportion = client_balances[client_id] / total_balance
+            actual_proportion = Decimal(sats) / Decimal(base_sats)
+            # Allow 1% tolerance for rounding
+            assert abs(actual_proportion - expected_proportion) < Decimal("0.01"), \
+                f"Client {client_id} proportion off: {actual_proportion} vs {expected_proportion}"
+
+
+# =============================================================================
+# MODEL CREATION TESTS
+# =============================================================================
+
+class TestModelCreation:
+    """Test that Pydantic models accept Decimal values correctly."""
+
+    def test_create_lamassu_transaction_data_with_decimals(self):
+        """Verify CreateLamassuTransactionData accepts Decimal values."""
+        tx = parse_csv_like_transaction_processor(LAMASSU_CSV_DATA["8.75pct_large"])
+
+        base_sats, commission_sats, effective = calculate_commission(
+            tx["crypto_amount"],
+            tx["commission_percentage"],
+            tx["discount"]
+        )
+        exchange_rate = calculate_exchange_rate(base_sats, tx["fiat_amount"])
+
+        # This should not raise any validation errors
+        data = CreateLamassuTransactionData(
+            lamassu_transaction_id=tx["transaction_id"],
+            fiat_amount=tx["fiat_amount"],
+            crypto_amount=tx["crypto_amount"],
+            commission_percentage=tx["commission_percentage"],
+            discount=tx["discount"],
+            effective_commission=effective,
+            commission_amount_sats=commission_sats,
+            base_amount_sats=base_sats,
+            exchange_rate=exchange_rate,
+            crypto_code=tx["crypto_code"],
+            fiat_code=tx["fiat_code"],
+            device_id=tx["device_id"],
+            transaction_time=tx["transaction_time"],
+        )
+
+        assert data.fiat_amount == Decimal("2000")
+        assert data.commission_percentage == Decimal("0.0875")
+        assert data.base_amount_sats == 284322
+        assert data.commission_amount_sats == 24878
+
+    def test_create_dca_payment_data_with_decimals(self):
+        """Verify CreateDcaPaymentData accepts Decimal values."""
+        tx = parse_csv_like_transaction_processor(LAMASSU_CSV_DATA["5.5pct_no_discount"])
+
+        base_sats, _, _ = calculate_commission(
+            tx["crypto_amount"],
+            tx["commission_percentage"],
+            tx["discount"]
+        )
+        exchange_rate = calculate_exchange_rate(base_sats, tx["fiat_amount"])
+
+        # Simulate a client getting half the distribution
+        client_sats = base_sats // 2
+        client_fiat = (Decimal(client_sats) / exchange_rate).quantize(Decimal("0.01"))
+
+        # This should not raise any validation errors
+        data = CreateDcaPaymentData(
+            client_id="test_client_123",
+            amount_sats=client_sats,
+            amount_fiat=client_fiat,
+            exchange_rate=exchange_rate,
+            transaction_type="flow",
+            lamassu_transaction_id=tx["transaction_id"],
+            transaction_time=tx["transaction_time"],
+        )
+
+        assert isinstance(data.amount_fiat, Decimal)
+        assert isinstance(data.exchange_rate, Decimal)
+        assert data.amount_sats == client_sats
+
+    def test_client_balance_summary_with_decimals(self):
+        """Verify ClientBalanceSummary accepts Decimal values."""
+        summary = ClientBalanceSummary(
+            client_id="test_client",
+            total_deposits=Decimal("5000.00"),
+            total_payments=Decimal("1234.56"),
+            remaining_balance=Decimal("3765.44"),
+            currency="GTQ",
+        )
+
+        assert summary.remaining_balance == Decimal("3765.44")
+        assert isinstance(summary.total_deposits, Decimal)
+
+
+# =============================================================================
+# EXCHANGE RATE PRECISION TESTS
+# =============================================================================
+
+class TestExchangeRatePrecision:
+    """Test that exchange rate calculations maintain precision."""
+
+    def test_exchange_rate_round_trip(self):
+        """Verify sats → fiat → sats round-trip maintains precision."""
+        tx = parse_csv_like_transaction_processor(LAMASSU_CSV_DATA["5.5pct_1300gtq_4clients"])
+
+        base_sats, _, _ = calculate_commission(
+            tx["crypto_amount"],
+            tx["commission_percentage"],
+            tx["discount"]
+        )
+
+        exchange_rate = calculate_exchange_rate(base_sats, tx["fiat_amount"])
+
+        # Convert sats to fiat and back
+        fiat_equivalent = Decimal(base_sats) / exchange_rate
+        sats_back = int((fiat_equivalent * exchange_rate).quantize(Decimal("1")))
+
+        # Should be within 1 sat of original
+        assert abs(sats_back - base_sats) <= 1
+
+    def test_per_client_fiat_sums_to_total(self):
+        """Verify per-client fiat amounts sum to total fiat (within tolerance)."""
+        tx = parse_csv_like_transaction_processor(LAMASSU_CSV_DATA["5.5pct_1300gtq_4clients"])
+
+        base_sats, _, _ = calculate_commission(
+            tx["crypto_amount"],
+            tx["commission_percentage"],
+            tx["discount"]
+        )
+
+        exchange_rate = calculate_exchange_rate(base_sats, tx["fiat_amount"])
+
+        client_balances = {
+            "client_a": Decimal("1"),
+            "client_b": Decimal("986"),
+            "client_c": Decimal("14"),
+            "client_d": Decimal("4"),
+        }
+
+        distributions = calculate_distribution(base_sats, client_balances)
+
+        # Calculate per-client fiat and sum
+        total_fiat_distributed = Decimal("0")
+        for client_id, sats in distributions.items():
+            client_fiat = (Decimal(sats) / exchange_rate).quantize(Decimal("0.01"))
+            total_fiat_distributed += client_fiat
+
+        # Should be within 0.05 GTQ of original (accounting for per-client rounding)
+        # This is the 0.01 discrepancy we discussed, multiplied by number of clients
+        assert abs(total_fiat_distributed - tx["fiat_amount"]) < Decimal("0.05"), \
+            f"Total distributed {total_fiat_distributed} vs original {tx['fiat_amount']}"
+
+
+# =============================================================================
+# CRUD LAYER TESTS (with mocked database)
+# =============================================================================
+
+class TestCrudLayerDecimalHandling:
+    """
+    Test that CRUD operations handle Decimal→float conversion for SQLite.
+
+    These tests mock the database layer to verify:
+    1. Decimal values from models are converted to float via prepare_for_db()
+    2. Float values from SQLite are converted back to Decimal via model validators
+    """
+
+    @pytest.mark.asyncio
+    async def test_create_deposit_passes_float_amount_for_sqlite(self):
+        """Verify create_deposit passes float amount to database (SQLite compatibility)."""
+        from unittest.mock import patch, AsyncMock
+
+        # Create deposit data with Decimal
+        deposit_data = CreateDepositData(
+            client_id="test_client_123",
+            amount=Decimal("1500.75"),
+            currency="GTQ",
+            notes="Test deposit"
+        )
+
+        # Verify the model stored it as Decimal
+        assert isinstance(deposit_data.amount, Decimal)
+        assert deposit_data.amount == Decimal("1500.75")
+
+        # Mock the database
+        mock_db = AsyncMock()
+        mock_db.execute = AsyncMock()
+        mock_db.fetchone = AsyncMock(return_value=DcaDeposit(
+            id="deposit_123",
+            client_id="test_client_123",
+            amount=1500.75,  # float from SQLite
+            currency="GTQ",
+            status="pending",
+            notes="Test deposit",
+            created_at=datetime.now(timezone.utc),
+            confirmed_at=None
+        ))
+
+        with patch('satmachineadmin.crud.db', mock_db):
+            from ..crud import create_deposit
+            result = await create_deposit(deposit_data)
+
+        # Verify db.execute was called
+        mock_db.execute.assert_called_once()
+
+        # Get the parameters passed to execute
+        call_args = mock_db.execute.call_args
+        params = call_args[0][1]  # Second positional arg is the params dict
+
+        # Verify the amount parameter is float (for SQLite compatibility)
+        assert isinstance(params["amount"], float)
+        assert params["amount"] == 1500.75
+
+    @pytest.mark.asyncio
+    async def test_create_dca_payment_passes_float_values_for_sqlite(self):
+        """Verify create_dca_payment passes float fiat and exchange_rate (SQLite compatibility)."""
+        from unittest.mock import patch, AsyncMock
+
+        # Parse a real transaction
+        tx = parse_csv_like_transaction_processor(LAMASSU_CSV_DATA["5.5pct_no_discount"])
+        base_sats, _, _ = calculate_commission(
+            tx["crypto_amount"],
+            tx["commission_percentage"],
+            tx["discount"]
+        )
+        exchange_rate = calculate_exchange_rate(base_sats, tx["fiat_amount"])
+
+        # Create payment data
+        client_sats = 146682  # Half of base
+        client_fiat = (Decimal(client_sats) / exchange_rate).quantize(Decimal("0.01"))
+
+        payment_data = CreateDcaPaymentData(
+            client_id="test_client",
+            amount_sats=client_sats,
+            amount_fiat=client_fiat,
+            exchange_rate=exchange_rate,
+            transaction_type="flow",
+            lamassu_transaction_id="def456",
+            transaction_time=tx["transaction_time"],
+        )
+
+        # Verify model has Decimal types
+        assert isinstance(payment_data.amount_fiat, Decimal)
+        assert isinstance(payment_data.exchange_rate, Decimal)
+
+        # Mock database - returns float like SQLite would
+        mock_db = AsyncMock()
+        mock_db.execute = AsyncMock()
+        mock_db.fetchone = AsyncMock(return_value=DcaPayment(
+            id="payment_123",
+            client_id="test_client",
+            amount_sats=client_sats,
+            amount_fiat=float(client_fiat),  # float from SQLite
+            exchange_rate=float(exchange_rate),  # float from SQLite
+            transaction_type="flow",
+            lamassu_transaction_id="def456",
+            payment_hash=None,
+            status="pending",
+            created_at=datetime.now(timezone.utc),
+            transaction_time=tx["transaction_time"],
+        ))
+
+        with patch('satmachineadmin.crud.db', mock_db):
+            from ..crud import create_dca_payment
+            result = await create_dca_payment(payment_data)
+
+        # Verify db.execute was called
+        mock_db.execute.assert_called_once()
+
+        # Get params
+        call_args = mock_db.execute.call_args
+        params = call_args[0][1]
+
+        # Verify float types in params (SQLite compatibility)
+        assert isinstance(params["amount_fiat"], float)
+        assert isinstance(params["exchange_rate"], float)
+
+    @pytest.mark.asyncio
+    async def test_create_lamassu_transaction_passes_floats_for_sqlite(self):
+        """Verify create_lamassu_transaction passes float fields (SQLite compatibility)."""
+        from unittest.mock import patch, AsyncMock
+
+        tx = parse_csv_like_transaction_processor(LAMASSU_CSV_DATA["8.75pct_large"])
+        base_sats, commission_sats, effective = calculate_commission(
+            tx["crypto_amount"],
+            tx["commission_percentage"],
+            tx["discount"]
+        )
+        exchange_rate = calculate_exchange_rate(base_sats, tx["fiat_amount"])
+
+        transaction_data = CreateLamassuTransactionData(
+            lamassu_transaction_id=tx["transaction_id"],
+            fiat_amount=tx["fiat_amount"],
+            crypto_amount=tx["crypto_amount"],
+            commission_percentage=tx["commission_percentage"],
+            discount=tx["discount"],
+            effective_commission=effective,
+            commission_amount_sats=commission_sats,
+            base_amount_sats=base_sats,
+            exchange_rate=exchange_rate,
+            crypto_code=tx["crypto_code"],
+            fiat_code=tx["fiat_code"],
+            device_id=tx["device_id"],
+            transaction_time=tx["transaction_time"],
+        )
+
+        # Verify all Decimal fields in the model
+        assert isinstance(transaction_data.fiat_amount, Decimal)
+        assert isinstance(transaction_data.commission_percentage, Decimal)
+        assert isinstance(transaction_data.discount, Decimal)
+        assert isinstance(transaction_data.effective_commission, Decimal)
+        assert isinstance(transaction_data.exchange_rate, Decimal)
+
+        # Mock database - returns floats like SQLite would
+        mock_db = AsyncMock()
+        mock_db.execute = AsyncMock()
+        mock_db.fetchone = AsyncMock(return_value=StoredLamassuTransaction(
+            id="tx_123",
+            lamassu_transaction_id=tx["transaction_id"],
+            fiat_amount=float(tx["fiat_amount"]),  # float from SQLite
+            crypto_amount=tx["crypto_amount"],
+            commission_percentage=float(tx["commission_percentage"]),  # float from SQLite
+            discount=float(tx["discount"]),  # float from SQLite
+            effective_commission=float(effective),  # float from SQLite
+            commission_amount_sats=commission_sats,
+            base_amount_sats=base_sats,
+            exchange_rate=float(exchange_rate),  # float from SQLite
+            crypto_code=tx["crypto_code"],
+            fiat_code=tx["fiat_code"],
+            device_id=tx["device_id"],
+            transaction_time=tx["transaction_time"],
+            processed_at=datetime.now(timezone.utc),
+            clients_count=0,
+            distributions_total_sats=0,
+        ))
+
+        with patch('satmachineadmin.crud.db', mock_db):
+            from ..crud import create_lamassu_transaction
+            result = await create_lamassu_transaction(transaction_data)
+
+        # Verify db.execute was called
+        mock_db.execute.assert_called_once()
+
+        # Get params
+        call_args = mock_db.execute.call_args
+        params = call_args[0][1]
+
+        # Verify all Decimal fields are converted to float for SQLite
+        assert isinstance(params["fiat_amount"], float), f"fiat_amount is {type(params['fiat_amount'])}"
+        assert isinstance(params["commission_percentage"], float)
+        assert isinstance(params["discount"], float)
+        assert isinstance(params["effective_commission"], float)
+        assert isinstance(params["exchange_rate"], float)
+
+        # Verify values match
+        assert params["fiat_amount"] == 2000.0
+        assert params["commission_percentage"] == 0.0875
+        assert params["base_amount_sats"] == 284322
+        assert params["commission_amount_sats"] == 24878
+
+    @pytest.mark.asyncio
+    async def test_client_balance_summary_returns_decimals(self):
+        """Verify get_client_balance_summary returns Decimal types."""
+        from unittest.mock import patch, AsyncMock
+
+        # Mock database responses
+        mock_db = AsyncMock()
+
+        # Mock deposits query result
+        mock_db.fetchone = AsyncMock(side_effect=[
+            # First call: deposits sum
+            {"total": Decimal("5000.00"), "currency": "GTQ"},
+            # Second call: payments sum
+            {"total": Decimal("1234.56")},
+        ])
+
+        with patch('satmachineadmin.crud.db', mock_db):
+            from ..crud import get_client_balance_summary
+            result = await get_client_balance_summary("test_client")
+
+        # Verify result has Decimal types
+        assert isinstance(result.total_deposits, Decimal)
+        assert isinstance(result.total_payments, Decimal)
+        assert isinstance(result.remaining_balance, Decimal)
+
+        # Verify values
+        assert result.total_deposits == Decimal("5000.00")
+        assert result.total_payments == Decimal("1234.56")
+        assert result.remaining_balance == Decimal("3765.44")
+
+
+# =============================================================================
+# SQLITE ROUND-TRIP TESTS
+# =============================================================================
+
+class TestSqliteDecimalRoundTrip:
+    """
+    Test that Decimal values survive the SQLite round-trip:
+    Decimal → float (prepare_for_db) → SQLite REAL → float → Decimal (validator)
+
+    SQLite doesn't support Decimal natively - it stores DECIMAL as REAL (float).
+    We use prepare_for_db() to convert Decimal→float before writing,
+    and Pydantic validators with pre=True to convert float→Decimal on read.
+    """
+
+    def test_prepare_for_db_converts_decimals_to_float(self):
+        """Verify prepare_for_db converts Decimal to float."""
+        from ..crud import prepare_for_db
+
+        values = {
+            "amount": Decimal("1500.75"),
+            "exchange_rate": Decimal("146.6825"),
+            "commission": Decimal("0.0875"),
+            "name": "test",  # Non-Decimal should pass through
+            "count": 42,  # Non-Decimal should pass through
+        }
+
+        result = prepare_for_db(values)
+
+        # Decimals should be converted to float
+        assert isinstance(result["amount"], float)
+        assert isinstance(result["exchange_rate"], float)
+        assert isinstance(result["commission"], float)
+
+        # Values should be preserved
+        assert result["amount"] == 1500.75
+        assert result["exchange_rate"] == 146.6825
+        assert result["commission"] == 0.0875
+
+        # Non-Decimals should pass through unchanged
+        assert result["name"] == "test"
+        assert result["count"] == 42
+
+    def test_model_validator_converts_float_to_decimal(self):
+        """Verify model validators convert float back to Decimal."""
+        # Simulate what comes back from SQLite (floats)
+        db_row = {
+            "id": "deposit_123",
+            "client_id": "client_abc",
+            "amount": 1500.75,  # float from SQLite
+            "currency": "GTQ",
+            "status": "pending",
+            "notes": "Test",
+            "created_at": datetime.now(timezone.utc),
+            "confirmed_at": None,
+        }
+
+        # Create model from "database" data
+        deposit = DcaDeposit(**db_row)
+
+        # Validator should have converted float → Decimal
+        assert isinstance(deposit.amount, Decimal)
+        assert deposit.amount == Decimal("1500.75")
+
+    def test_payment_model_converts_multiple_floats(self):
+        """Verify DcaPayment converts all float fields to Decimal."""
+        db_row = {
+            "id": "payment_123",
+            "client_id": "client_abc",
+            "amount_sats": 146682,
+            "amount_fiat": 1000.50,  # float from SQLite
+            "exchange_rate": 146.6825,  # float from SQLite
+            "transaction_type": "flow",
+            "lamassu_transaction_id": "tx_456",
+            "payment_hash": None,
+            "status": "confirmed",
+            "created_at": datetime.now(timezone.utc),
+            "transaction_time": datetime.now(timezone.utc),
+        }
+
+        payment = DcaPayment(**db_row)
+
+        assert isinstance(payment.amount_fiat, Decimal)
+        assert isinstance(payment.exchange_rate, Decimal)
+        assert payment.amount_fiat == Decimal("1000.50")
+        assert payment.exchange_rate == Decimal("146.6825")
+
+    def test_stored_transaction_converts_all_decimal_fields(self):
+        """Verify StoredLamassuTransaction converts all float fields."""
+        db_row = {
+            "id": "tx_123",
+            "lamassu_transaction_id": "lamassu_abc",
+            "fiat_amount": 2000.00,  # float from SQLite
+            "crypto_amount": 309200,
+            "commission_percentage": 0.0875,  # float from SQLite
+            "discount": 0.0,  # float from SQLite
+            "effective_commission": 0.0875,  # float from SQLite
+            "commission_amount_sats": 24878,
+            "base_amount_sats": 284322,
+            "exchange_rate": 142.161,  # float from SQLite
+            "crypto_code": "BTC",
+            "fiat_code": "GTQ",
+            "device_id": "device1",
+            "transaction_time": datetime.now(timezone.utc),
+            "processed_at": datetime.now(timezone.utc),
+            "clients_count": 2,
+            "distributions_total_sats": 284322,
+        }
+
+        tx = StoredLamassuTransaction(**db_row)
+
+        # All Decimal fields should be converted
+        assert isinstance(tx.fiat_amount, Decimal)
+        assert isinstance(tx.commission_percentage, Decimal)
+        assert isinstance(tx.discount, Decimal)
+        assert isinstance(tx.effective_commission, Decimal)
+        assert isinstance(tx.exchange_rate, Decimal)
+
+        # Values should be preserved
+        assert tx.fiat_amount == Decimal("2000.00")
+        assert tx.commission_percentage == Decimal("0.0875")
+        assert tx.discount == Decimal("0.0")
+        assert tx.effective_commission == Decimal("0.0875")
+
+    def test_full_round_trip_preserves_precision(self):
+        """
+        Test complete round-trip: Decimal → prepare_for_db → float → Decimal.
+
+        This simulates what happens in production:
+        1. We have Decimal values from calculations
+        2. prepare_for_db converts them to float for SQLite
+        3. SQLite stores as REAL
+        4. We read back as float
+        5. Model validators convert back to Decimal
+        """
+        from ..crud import prepare_for_db
+
+        # Original Decimal values (from calculations)
+        original = {
+            "fiat_amount": Decimal("1300.00"),
+            "commission_percentage": Decimal("0.055"),
+            "discount": Decimal("0"),
+            "effective_commission": Decimal("0.055"),
+            "exchange_rate": Decimal("149.90215490109"),  # High precision
+        }
+
+        # Step 1: Convert for database storage
+        for_db = prepare_for_db(original)
+
+        # Verify all are floats
+        for key in original:
+            assert isinstance(for_db[key], float), f"{key} should be float"
+
+        # Step 2: Simulate SQLite storage and retrieval
+        # (SQLite would store these as REAL and return as float)
+        from_db = for_db.copy()
+
+        # Step 3: Create a model (simulating what happens when reading)
+        db_row = {
+            "id": "tx_test",
+            "lamassu_transaction_id": "test_123",
+            "fiat_amount": from_db["fiat_amount"],
+            "crypto_amount": 205600,
+            "commission_percentage": from_db["commission_percentage"],
+            "discount": from_db["discount"],
+            "effective_commission": from_db["effective_commission"],
+            "commission_amount_sats": 10718,
+            "base_amount_sats": 194882,
+            "exchange_rate": from_db["exchange_rate"],
+            "crypto_code": "BTC",
+            "fiat_code": "GTQ",
+            "device_id": "device1",
+            "transaction_time": datetime.now(timezone.utc),
+            "processed_at": datetime.now(timezone.utc),
+            "clients_count": 1,
+            "distributions_total_sats": 194882,
+        }
+
+        tx = StoredLamassuTransaction(**db_row)
+
+        # Step 4: Verify Decimal types restored
+        assert isinstance(tx.fiat_amount, Decimal)
+        assert isinstance(tx.commission_percentage, Decimal)
+        assert isinstance(tx.exchange_rate, Decimal)
+
+        # Step 5: Verify precision for 2 decimal place values
+        assert tx.fiat_amount == Decimal("1300.0")  # SQLite preserves this exactly
+        assert tx.commission_percentage == Decimal("0.055")
+        assert tx.discount == Decimal("0.0")
+
+    def test_client_balance_summary_float_conversion(self):
+        """Verify ClientBalanceSummary converts floats from aggregation queries."""
+        # SQLite SUM() returns float
+        db_row = {
+            "client_id": "client_123",
+            "total_deposits": 5000.00,  # float from SUM()
+            "total_payments": 1234.56,  # float from SUM()
+            "remaining_balance": 3765.44,  # calculated float
+            "currency": "GTQ",
+        }
+
+        summary = ClientBalanceSummary(**db_row)
+
+        assert isinstance(summary.total_deposits, Decimal)
+        assert isinstance(summary.total_payments, Decimal)
+        assert isinstance(summary.remaining_balance, Decimal)
+        assert summary.remaining_balance == Decimal("3765.44")
diff --git a/transaction_processor.py b/transaction_processor.py
index 45e0880..deaac47 100644
--- a/transaction_processor.py
+++ b/transaction_processor.py
@@ -3,6 +3,7 @@
 import asyncio
 import asyncpg
 from datetime import datetime, timedelta, timezone
+from decimal import Decimal
 from typing import List, Optional, Dict, Any
 from loguru import logger
 import socket
@@ -492,28 +493,38 @@ class LamassuTransactionProcessor:
                     results = []
                     for row in reader:
                         # Convert string values to appropriate types
+                        # Use Decimal for monetary and percentage values
                         processed_row = {}
                         for key, value in row.items():
                             # Handle None/empty values consistently at data ingestion boundary
                             if value == '' or value is None:
-                                if key in ['fiat_amount', 'crypto_amount']:
-                                    processed_row[key] = 0  # Default numeric fields to 0
+                                if key == 'crypto_amount':
+                                    processed_row[key] = 0  # Sats are always int
+                                elif key == 'fiat_amount':
+                                    processed_row[key] = Decimal("0")  # Fiat as Decimal
                                 elif key in ['commission_percentage', 'discount']:
-                                    processed_row[key] = 0.0  # Default percentage fields to 0.0
+                                    processed_row[key] = Decimal("0")  # Percentages as Decimal
                                 else:
                                     processed_row[key] = None  # Keep None for non-numeric fields
                             elif key in ['transaction_id', 'device_id', 'crypto_code', 'fiat_code']:
                                 processed_row[key] = str(value)
-                            elif key in ['fiat_amount', 'crypto_amount']:
+                            elif key == 'crypto_amount':
                                 try:
-                                    processed_row[key] = int(float(value))
+                                    processed_row[key] = int(float(value))  # Sats are always int
                                 except (ValueError, TypeError):
-                                    processed_row[key] = 0  # Fallback to 0 for invalid values
+                                    processed_row[key] = 0
+                            elif key == 'fiat_amount':
+                                try:
+                                    # Convert via string to avoid float precision issues
+                                    processed_row[key] = Decimal(str(value))
+                                except (ValueError, TypeError):
+                                    processed_row[key] = Decimal("0")
                             elif key in ['commission_percentage', 'discount']:
                                 try:
-                                    processed_row[key] = float(value)
+                                    # Convert via string to avoid float precision issues
+                                    processed_row[key] = Decimal(str(value))
                                 except (ValueError, TypeError):
-                                    processed_row[key] = 0.0  # Fallback to 0.0 for invalid values
+                                    processed_row[key] = Decimal("0")
                             elif key == 'transaction_time':
                                 from datetime import datetime
                                 # Parse PostgreSQL timestamp format and ensure it's in UTC for consistency
@@ -679,13 +690,13 @@ class LamassuTransactionProcessor:
                 logger.info("No Flow Mode clients found - skipping distribution")
                 return {}
             
-            # Extract transaction details - guaranteed clean from data ingestion
+            # Extract transaction details - guaranteed clean from data ingestion (Decimal types)
             crypto_atoms = transaction.get("crypto_amount", 0)  # Total sats with commission baked in
-            fiat_amount = transaction.get("fiat_amount", 0)     # Actual fiat dispensed (principal only)
-            commission_percentage = transaction.get("commission_percentage", 0.0)  # Already stored as decimal (e.g., 0.045)
-            discount = transaction.get("discount", 0.0)  # Discount percentage
+            fiat_amount = transaction.get("fiat_amount", Decimal("0"))     # Actual fiat dispensed (principal only)
+            commission_percentage = transaction.get("commission_percentage", Decimal("0"))  # Already stored as Decimal (e.g., 0.045)
+            discount = transaction.get("discount", Decimal("0"))  # Discount percentage
             transaction_time = transaction.get("transaction_time")  # ATM transaction timestamp for temporal accuracy
-            
+
             # Normalize transaction_time to UTC if present
             if transaction_time is not None:
                 if transaction_time.tzinfo is None:
@@ -697,7 +708,7 @@ class LamassuTransactionProcessor:
                     original_tz = transaction_time.tzinfo
                     transaction_time = transaction_time.astimezone(timezone.utc)
                     logger.info(f"Converted transaction time from {original_tz} to UTC")
-            
+
             # Validate required fields
             if crypto_atoms is None:
                 logger.error(f"Missing crypto_amount in transaction: {transaction}")
@@ -707,10 +718,10 @@ class LamassuTransactionProcessor:
                 return {}
             if commission_percentage is None:
                 logger.warning(f"Missing commission_percentage in transaction: {transaction}, defaulting to 0")
-                commission_percentage = 0.0
+                commission_percentage = Decimal("0")
             if discount is None:
                 logger.info(f"Missing discount in transaction: {transaction}, defaulting to 0")
-                discount = 0.0
+                discount = Decimal("0")
             if transaction_time is None:
                 logger.warning(f"Missing transaction_time in transaction: {transaction}")
                 # Could use current time as fallback, but this indicates a data issue
@@ -733,15 +744,16 @@ class LamassuTransactionProcessor:
                 logger.warning("No transaction time available - using current balances (may be inaccurate)")
             
             # Get balance summaries for all clients to calculate proportions
-            client_balances = {}
-            total_confirmed_deposits = 0
-            
+            client_balances: Dict[str, Decimal] = {}
+            total_confirmed_deposits = Decimal("0")
+            min_balance = Decimal("0.01")
+
             for client in flow_clients:
                 # Get balance as of the transaction time for temporal accuracy
                 balance = await get_client_balance_summary(client.id, as_of_time=transaction_time)
                 # Only include clients with positive remaining balance
                 # NOTE: This works for fiat amounts that use cents
-                if balance.remaining_balance >= 0.01:
+                if balance.remaining_balance >= min_balance:
                     client_balances[client.id] = balance.remaining_balance
                     total_confirmed_deposits += balance.remaining_balance
                     logger.debug(f"Client {client.id[:8]}... included with balance: {balance.remaining_balance:.2f} GTQ")
@@ -766,7 +778,10 @@ class LamassuTransactionProcessor:
                 proportion = client_balances[client_id] / total_confirmed_deposits
 
                 # Calculate equivalent fiat value in GTQ for tracking purposes
-                client_fiat_amount = round(client_sats_amount / exchange_rate, 2) if exchange_rate > 0 else 0.0
+                if exchange_rate > 0:
+                    client_fiat_amount = (Decimal(client_sats_amount) / exchange_rate).quantize(Decimal("0.01"))
+                else:
+                    client_fiat_amount = Decimal("0")
 
                 distributions[client_id] = {
                     "fiat_amount": client_fiat_amount,
@@ -920,7 +935,7 @@ class LamassuTransactionProcessor:
             }
             new_payment = await create_invoice(
                 wallet_id=target_wallet.id,
-                amount=amount_sats,  # LNBits create_invoice expects sats
+                amount=float(amount_sats),  # LNBits expects float for amount
                 internal=True,  # Internal transfer within LNBits
                 memo=memo,
                 extra=extra
@@ -1003,20 +1018,20 @@ class LamassuTransactionProcessor:
     async def store_lamassu_transaction(self, transaction: Dict[str, Any]) -> Optional[str]:
         """Store the Lamassu transaction in our database for audit and UI"""
         try:
-            # Extract transaction data - guaranteed clean from data ingestion boundary
+            # Extract transaction data - guaranteed clean from data ingestion boundary (Decimal types)
             crypto_atoms = transaction.get("crypto_amount", 0)
-            fiat_amount = transaction.get("fiat_amount", 0)
-            commission_percentage = transaction.get("commission_percentage", 0.0)
-            discount = transaction.get("discount", 0.0)
+            fiat_amount = transaction.get("fiat_amount", Decimal("0"))
+            commission_percentage = transaction.get("commission_percentage", Decimal("0"))
+            discount = transaction.get("discount", Decimal("0"))
             transaction_time = transaction.get("transaction_time")
-            
+
             # Normalize transaction_time to UTC if present
             if transaction_time is not None:
                 if transaction_time.tzinfo is None:
                     transaction_time = transaction_time.replace(tzinfo=timezone.utc)
                 elif transaction_time.tzinfo != timezone.utc:
                     transaction_time = transaction_time.astimezone(timezone.utc)
-            
+
             # Calculate commission metrics using the extracted pure function
             base_crypto_atoms, commission_amount_sats, effective_commission = calculate_commission(
                 crypto_atoms, commission_percentage, discount
@@ -1024,11 +1039,13 @@ class LamassuTransactionProcessor:
 
             # Calculate exchange rate
             exchange_rate = calculate_exchange_rate(base_crypto_atoms, fiat_amount)
-            
-            # Create transaction data with GTQ amounts
+
+            # Create transaction data with GTQ amounts (Decimal already, just ensure 2 decimal places)
+            fiat_amount_rounded = fiat_amount.quantize(Decimal("0.01")) if isinstance(fiat_amount, Decimal) else Decimal(str(fiat_amount)).quantize(Decimal("0.01"))
+
             transaction_data = CreateLamassuTransactionData(
                 lamassu_transaction_id=transaction["transaction_id"],
-                fiat_amount=round(fiat_amount, 2),  # Store GTQ with 2 decimal places
+                fiat_amount=fiat_amount_rounded,
                 crypto_amount=crypto_atoms,
                 commission_percentage=commission_percentage,
                 discount=discount,
@@ -1085,7 +1102,7 @@ class LamassuTransactionProcessor:
             
             commission_payment = await create_invoice(
                 wallet_id=admin_config.commission_wallet_id,
-                amount=commission_amount_sats,
+                amount=float(commission_amount_sats),  # LNBits expects float
                 internal=True,
                 memo=commission_memo,
                 extra={
@@ -1148,9 +1165,9 @@ class LamassuTransactionProcessor:
             
             # Calculate commission amount for sending to commission wallet
             crypto_atoms = transaction.get("crypto_amount", 0)
-            commission_percentage = transaction.get("commission_percentage", 0.0)
-            discount = transaction.get("discount", 0.0)
-            
+            commission_percentage = transaction.get("commission_percentage", Decimal("0"))
+            discount = transaction.get("discount", Decimal("0"))
+
             # Calculate commission amount using the extracted pure function
             _, commission_amount_sats, _ = calculate_commission(
                 crypto_atoms, commission_percentage, discount