diff --git a/models.py b/models.py
index 8be64c9..c8632d0 100644
--- a/models.py
+++ b/models.py
@@ -51,7 +51,11 @@ class CreateAccount(BaseModel):
 class CreateChartAccount(BaseModel):
     """Admin-created chart-of-accounts entry written to accounts/chart.beancount."""
     name: str  # Full hierarchical account name, e.g. "Expenses:Services:Domain"
-    currencies: list[str] = ["EUR", "SATS", "USD"]
+    # Optional currency constraint. Omitted by the UI: an Open directive needs
+    # no currency list, and constraining it would reject postings in other
+    # currencies (the CAD/GBP/JPY bean-check errors we saw on user accounts).
+    # None → unconstrained Open; a list → explicit constraint for API callers.
+    currencies: Optional[list[str]] = None
     description: Optional[str] = None