Skip to content
PayOps Kit
Donate

ACH Notification of Change code

C01 NOC code: Incorrect DFI Account Number

An RDFI sends C01 instead of returning an entry it could post but that carried outdated or wrong information. Corrected data: Correct DFI Account Number in positions 1–17.

What C01 means

C01 is the change code Incorrect DFI Account Number. The entry it answers was posted (or, for a prenotification, accepted); the NOC tells the Originator what to correct before the next one.

  • The account number in the entry is wrong but the RDFI could still identify the account (by name, or an old number it recognizes).
  • The bank converted its account numbers and the old one still posts for now.

What to update, and by when

Replace the stored DFI Account Number with the corrected one.

The Rules give the Originator six banking days from receiving the NOC information, or until its next entry to the account, whichever is later. NOCs carry no money: the entry they answer settled normally.

The RDFI transmits the NOC within 2 banking days of the settlement date of the original entry; the Originator makes the change within 6 banking days of receiving the NOC information or before its next entry, whichever is later.

Worked example

For an entry that settled on Wednesday, November 25, 2026, the day before Thanksgiving: the RDFI must transmit the NOC by Monday, November 30, 2026.

Try your own settlement date in the ACH date calculator

How C01 appears in a NACHA file

A NOC is a zero-dollar entry in a batch with SEC code COR. Its entry detail record carries a return-type transaction code (21, 26, 31 or 36) and one addenda record of type 98:

Notification of Change addenda record (type 98) with C01
PositionsFieldIn a C01 NOC
1Record Type Code7 (addenda)
2–3Addenda Type Code98 (Notification of Change)
4–6Change CodeC01
7–21Original Entry Trace NumberTrace number of the entry being corrected
22–27ReservedBlank
28–35Original Receiving DFI IdentificationFirst 8 digits of the original entry’s RDFI routing number
36–64Corrected DataCorrect DFI Account Number in positions 1–17
65–79ReservedBlank
80–94Trace NumberThe NOC entry’s own trace number

To read a NOC file record by record, open the file in NACHA Navigator, a free sister site that parses NACHA files in your browser without uploading them.

Look up C01 from code or an AI agent

REST · GET · no key
curl -s 'https://payopskit.com/api/v1/codes/C01?set=ach-noc'
MCP · tools/call · lookup_payment_code
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "lookup_payment_code",
    "arguments": {
      "code": "C01",
      "set": "ach-noc"
    }
  }
}
Response (JSON)
{
  "code": "C01",
  "set": "ach-noc",
  "found": true,
  "matches": [
    {
      "set": "ach-noc",
      "code": "C01",
      "name": "Incorrect DFI Account Number",
      "description": "Notification of Change. Corrected data: Correct DFI Account Number in positions 1–17.",
      "details": {
        "refused": false,
        "retired": false,
        "correctedData": "Correct DFI Account Number in positions 1–17",
        "timeframe": "The RDFI transmits the NOC within 2 banking days of the settlement date of the original entry; the Originator makes the change within 6 banking days of receiving the NOC information or before its next entry, whichever is later",
        "timeframeKind": "banking-days",
        "timeframeDays": 2,
        "caveat": null
      }
    }
  ]
}

The MCP server is at /mcp (Streamable HTTP, no key); the API and MCP docs show how to connect Claude, Cursor or VS Code.

Source: Nacha Operating Rules, Appendix Five (Notification of Change). The code’s title is the Rules’ own; the rest is this site’s plain-language summary, informational and not a substitute for the Rules or your ODFI agreement.