ACH Standard Entry Class code

COR SEC code: Notification of Change or Refused Notification of Change

Zero-dollar entry correcting information in an earlier entry.

What COR is for

Notifications of Change (C01–C14, of which C04 and C10–C12 are retired): zero-dollar entries telling the Originator to correct details such as an account or routing number.
Refused Notifications of Change (C61–C69), sent back when a NOC itself is wrong.

Sent by an RDFI (NOC) or an ODFI (refused NOC) about an earlier entry.

Authorization

None needed: COR entries correct information about entries already authorized.

A summary in general terms: the Nacha Operating Rules set the exact requirements, and Regulation E adds its own for consumer accounts.

Debits, credits and addenda

Zero-dollar entries only.

Addenda on a forward entry: type 98, exactly 1 per entry. Returns (addenda type 99) and Notifications of Change (type 98) follow their own layouts whatever the SEC code.

Returns

The general return timeframes apply: 2 banking days after settlement for most codes, with the account-type rules of the entry’s Receiver.

Common mix-ups

A NOC (COR) corrects details while the money still moves; a return sends the money back.

Where COR sits in a NACHA file

The SEC code is a batch-level field: positions 51–53 of the Company/Batch Header record (type 5), so every entry in the batch shares it, and a file that mixes SEC codes puts them in separate batches. The batch header also carries the Company Name, Company Identification and Company Entry Description that Receivers see on their statements.

To read a COR batch 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 COR from code or an AI agent

REST · GET · no key

curl -s 'https://payopskit.com/api/v1/codes/COR?set=ach-sec'

MCP · tools/call · lookup_payment_code

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "lookup_payment_code",
    "arguments": {
      "code": "COR",
      "set": "ach-sec"
    }
  }
}

Response (JSON)

{
  "code": "COR",
  "set": "ach-sec",
  "found": true,
  "matches": [
    {
      "set": "ach-sec",
      "code": "COR",
      "name": "Notification of Change or Refused Notification of Change",
      "description": "Zero-dollar entry correcting information in an earlier entry.",
      "details": {
        "direction": "zero",
        "addendaTypes": "98",
        "minAddenda": 1,
        "maxAddenda": 1
      }
    }
  ]
}

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 Three (Standard Entry Class codes). The code’s name 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.