Bank-Account Check Digits: Why Supplier Payments Are Rejected

A check-digit algorithm is meant to catch typing mistakes in the account-number structure before payment is sent. It does not prove that an account belongs to the supplier, that the supplier authorized the details, or that the payment is allowed. Confusing these three controls is why a system can call data “valid” while a payment still fails or reaches the wrong party.

Keep three controls separate

First, validate structure: bank, branch, account, and the approved validation method for the payment route. Second, validate changes: any bank-detail update should arrive from an agreed source, receive second-person approval, and retain evidence. Third, check the batch: show every payment whose bank account changed since the previous payment.

Return a useful message rather than “invalid account,” such as missing branch, unexpected length, or failed structure validation. Never expose a full account number in alerts or send it through WhatsApp for “verification.”

If a structure check fails, do not guess a correction. If it passes but account details changed, do not auto-approve payment. A check digit is an input-error filter, not proof of account ownership.

Source

MASAV file specifications and guidance