Handle ACH Notifications of Change (NOC, COR entries, C-codes) as an originator to update stored account data before re-originating

Verified steps

1. Ingest NOC entries delivered by your ODFI in the daily ACH returns file or via your BaaS provider's webhook (event type varies by provider; Modern Treasury emits a return event with a specific return code in the C01-C07 range); parse the Corrected Data field in the addenda record which contains the corrected routing number, account number, or transaction code
2. Map each C-code to the specific field that requires correction: C01 (incorrect account number — update account number), C02 (incorrect routing number — update routing number), C03 (incorrect account number and routing number — update both), C05 (incorrect transaction code — update debit/credit type), C06 (incorrect account number and transaction code — update both), C07 (incorrect routing number, account number, and transaction code — update all three)
3. Update your stored customer account record with the corrected data before initiating any subsequent ACH entry to that account; NACHA rules require you to make corrections within six banking days of NOC receipt or prior to the next origination to that account, whichever is later
4. Log the NOC event with timestamp, original values, corrected values, and the source RDFI routing number for audit trail purposes; trigger a customer notification if the correction changes account details that the customer provided
5. Do not retry a failed payment immediately after receiving an NOC — the NOC may arrive after a return on the same entry; process the return first, then apply the NOC correction, then re-originate with corrected data
6. Monitor NOC volume per customer account; repeated NOCs for the same account may indicate data quality issues or account takeover and should trigger enhanced review before further origination