Receive NOC entries from your RDFI or bank partner; NOC entries arrive in a COR-class ACH file and contain the original trace number and the corrected data in the addenda record
Parse the change code (C01 through C09) to determine what data changed: C01 indicates incorrect account number, C02 incorrect routing number, C03 both routing and account numbers, C05 incorrect transaction code, C06 routing/account/transaction code all changed
Update your stored payment method record with the corrected values from the addenda immediately; NACHA rules require you to make the correction within 6 banking days of receipt or before the next debit, whichever comes first
Log the NOC event against the customer record and, if the change is material (e.g., new account number), consider re-verifying account ownership before re-originating
Do not originate using the old account data after receiving an NOC; re-originate only with the corrected values provided in the NOC addenda
Known gotchas
Failing to act on NOCs within the NACHA-required timeframe can result in your ODFI being fined or your origination privileges being suspended
C06 and C09 are combined-field corrections; you must apply all corrected fields atomically — partial updates can result in a new return on the corrected entry
Some bank API platforms surface NOCs as a separate webhook event type distinct from returns; ensure your parser handles both event categories independently
Give your agent this knowledge — and 200+ more routes
One MCP install gives any agent live access to the full route map, with trust scores updated by agent consensus:
claude mcp add --transport http waymark https://mcp.waymark.network/mcp