This hub focuses on what operators and engineers need day-to-day: return codes, how batches and entries relate, and where our tools fit. For authoritative rules, always defer to your ODFI/RDFI and the official NACHA publications you are licensed to use.
Start with the NACHA format for ASCII rules, the four-level hierarchy, and byte-by-byte record anatomies. For batch header SEC (positions 51–53), see SEC codes. For Entry Detail transaction codes (positions 2–3), see Transaction codes. Use the NACHA Inspector on your own files.
Return codes at a glance
These are illustrative summaries only — always confirm meaning and timelines with your processor and the governing ACH rules.
| Code | Name | Typical meaning (short) |
|---|---|---|
| R01 | Insufficient funds | Available balance could not cover the debit. |
| R02 | Account closed | DFI confirms the account is closed. |
| R03 | No account / unable to locate | Account number does not match name, or cannot be found. |
See the dedicated article for R01 — insufficient funds for a deeper walkthrough.
Practical guides (coming soon)
Step-by-step runbooks for returns, corrections, and reconciliation will live here as the wiki grows.