What is an ACH return and what causes it?

An ACH return happens when a payment processed through the Automated Clearing House network gets rejected and reversed. The rejection comes from the receiving bank within a window that varies by reason code — most commonly 2 business days for unauthorized transactions, longer for some other categories. The funds, if they were ever credited, get pulled back from the merchant.

Common reasons for ACH returns: insufficient funds (R01), bank account closed (R02), no account at the destination bank (R03), invalid account number (R04), unauthorized transaction (R10), customer-requested stop payment (R08), and corporate authorization revoked (R29). Each return code has different operational implications — some are recoverable with a fresh payment attempt, others mean the account is permanently unusable.

ACH returns differ from check NSF events in two ways. First, the timeline is faster — most ACH returns settle within 2-3 business days, while bounced checks can take a week or more to fully reverse. Second, the customer experience is different — many ACH returns happen silently from the customer's perspective, so a follow-up communication is required to alert them and request a fresh payment method.