PlinthRail

ACH

Practical ACH reference for operators and engineers: return codes, NOC codes, file layout, and how PlinthRail tools map to NACHA concepts.

Reference hub Last updated May 6, 2026

ACH return codes

Operator-friendly explanations of common return codes, with remediation patterns and links to specs.

ACH NOC codes

Notification of Change reference (C01–C14 plus refused NOCs C61–C69) with fields to correct and 6-banking-day handling timing.

Acknowledge file

FedACH ACK file guide: status semantics, key fields, and operator response interpretation.

NACHA format

ASCII rules, 94-byte records, hierarchy, and field-by-field anatomies — plus the Inspector for live files.

SEC codes

Standard Entry Class map: consumer, B2B, check conversion, and IAT — with comparisons and batch-header context.

Transaction codes

Entry Detail transaction codes (positions 2–3): account type × purpose matrix, prenotes, zero-dollar, returns, GL and loan.

Special cases

Practical handling notes for ACH edge workflows: reversals, returns, micro-validation, prenotes, and zero-dollar remittance entries.

NACHA inspector (client-side)

Parse and explore ACH files entirely in the browser for quick triage and education.

Explore in your browser

Use the NACHA Inspector to review file structure and entry fields locally — files never leave your device.

Open NACHA Inspector

This hub focuses on what operators and engineers need day-to-day: return codes, NOC 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. For operator acknowledgment responses, see Acknowledge file. Use the NACHA Inspector and FedLine ACK Parser on your own files.

Return codes vs. NOC codes

Return codes (R-series) reject an entry — the funds do not move (or are clawed back). NOC codes (C-series) do not reject anything; they tell the Originator to update Receiver information so subsequent entries are correct. Both flow through Addenda records, but they signal different obligations and different time frames.

Return codes at a glance

These are illustrative summaries only — always confirm meaning and timelines with your processor and the governing ACH rules.

CodeNameTypical meaning (short)
R01Insufficient fundsAvailable balance could not cover the debit.
R02Account closedDFI confirms the account is closed.
R03No account / unable to locateAccount number does not match name, or cannot be found.
R04Invalid account number structureAccount/routing detail is structurally invalid.
R08Payment stoppedReceiver placed stop payment on a specific debit.
R09Uncollected fundsLedger balance exists but available funds are insufficient.
R10Customer advises not authorizedReceiver says debit is unauthorized/originator unknown.
R11Entry not in accordance with authorizationAmount/date/terms differ from authorization.
R16Account frozen / OFAC returnAccount is restricted by legal or compliance controls.
R29Corporate customer advises not authorizedCorporate receiver disputes CCD/CTX debit authorization.

For full detail by code (official description, initiator, window, direction, and reinitiation notes), open ACH return codes.

NOC codes at a glance

CodeNameWhat to update
C01Incorrect DFI Account NumberAccount number on Receiver record.
C02Incorrect Routing NumberRouting number on Receiver record.
C03Incorrect Routing Number and Account NumberBoth routing and account number.
C05Incorrect Transaction CodeAccount-type code (checking ↔ savings).
C07Routing + Account + Transaction CodeAll three fields (typical post-merger NOC).
C09Incorrect Individual ID NumberIndividual identifier on Receiver record.
C13Addenda Format ErrorUpstream ACH file builder.
C14Incorrect SEC for Outbound InternationalSwitch SEC code to IAT before next entry.

For the full set, including refused NOCs (C61–C69) and the 6-banking-day rule, open ACH NOC codes.