diff --git a/src/modules/expenses/types/index.ts b/src/modules/expenses/types/index.ts
index 5ce4932..1f9e37e 100644
--- a/src/modules/expenses/types/index.ts
+++ b/src/modules/expenses/types/index.ts
@@ -51,12 +51,12 @@ export enum PermissionType {
  */
 export interface ExpenseEntryRequest {
   description: string
-  amount: number // In sats
+  amount: number // Amount in the specified currency (or satoshis if currency is None)
   expense_account: string // Account name or ID
   is_equity: boolean
   user_wallet: string
   reference?: string
-  currency?: string // e.g., "USD"
+  currency?: string // If None, amount is in satoshis. Otherwise, fiat currency code (e.g., "EUR", "USD")
   entry_date?: string // ISO datetime string
 }