Build a cash sweep product that moves end-of-day excess balances into a money market fund and sweeps back each morning using Modern Treasury

Steps

1. Define the sweep logic: calculate end-of-day available balance from Modern Treasury's account balance endpoint, subtract the target operating balance, and determine the sweep amount (positive for sweep-out, negative for sweep-back)
2. Originate the sweep-out as a payment order in Modern Treasury with direction debit, targeting the money market fund's bank account; record the payment order ID and link it to a ledger transaction that debits the operating account and credits a money market investment account
3. On the morning sweep-back, check the money market fund's settlement confirmation (via webhook or polling); originate a reverse payment order to pull funds back into the operating account
4. Post corresponding ledger transactions for the sweep-back: debit the money market investment account and credit the operating account, recording the accrued interest as a separate credit to an interest income ledger account
5. Implement holiday and weekend handling: do not originate sweep transfers on days when ACH is not processing; maintain a business day calendar and skip sweep origination on non-settlement days
6. Run a daily reconciliation that compares the money market fund's reported NAV (from the fund's statement or API) against your internal investment ledger balance; alert on any discrepancy