ACH return reason code
R26 return code: Mandatory Field Error
A mandatory field is missing or invalid.
What R26 means
R26 is the return reason code Mandatory Field Error
. A mandatory field is missing or invalid.
It is sent by the ACH Operator or RDFI as a return entry: the original entry goes back to the ODFI with an addenda record carrying R26, and the ODFI passes the return on to the Originator.
Typical causes
- A field the Rules make mandatory for this SEC code is blank or invalid.
Return timeframe
ACH Operator: next file delivery after processing; an RDFI using it has the general 2 banking days after the settlement date of the original entry.
Banking days are the Federal Reserve’s business days: weekends and Fed holidays don’t count, so a holiday in the window pushes the deadline out by a day.
Worked example
For an entry that settled on Wednesday, November 25, 2026, the day before Thanksgiving: must be available to the ODFI by opening of business on Monday, November 30, 2026.
What the Originator can do next
- Fix whatever builds the file so every mandatory field is filled, then send the entry again.
How R26 appears in a NACHA file
A return is the original entry detail record (type 6) sent back with a return transaction code — 21 or 26 for a checking account, 31 or 36 for savings (21 and 31 return a credit, 26 and 36 a debit) — the original amount, and an addenda record of type 99 that carries the reason. The batch keeps the original entry’s SEC code.
| Positions | Field | In an R26 return |
|---|---|---|
| 1 | Record Type Code | 7 (addenda) |
| 2–3 | Addenda Type Code | 99 (return) |
| 4–6 | Return Reason Code | R26 |
| 7–21 | Original Entry Trace Number | Trace number of the entry being returned |
| 22–27 | Date of Death | YYMMDD for R14 and R15; blank otherwise |
| 28–35 | Original Receiving DFI Identification | First 8 digits of the original entry’s RDFI routing number |
| 36–79 | Addenda Information | Free text from the RDFI |
| 80–94 | Trace Number | The return entry’s own trace number |
To read a return 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 R26 from code or an AI agent
The code table on this page is the one behind the REST API and the MCP server, so a script or an AI agent gets the same answer as JSON. No key and no account.
curl -s 'https://payopskit.com/api/v1/codes/R26?set=ach-return'{
"jsonrpc": "2.0",
"id": 1,
"method": "tools/call",
"params": {
"name": "lookup_payment_code",
"arguments": {
"code": "R26",
"set": "ach-return"
}
}
}{
"code": "R26",
"set": "ach-return",
"found": true,
"matches": [
{
"set": "ach-return",
"code": "R26",
"name": "Mandatory Field Error",
"description": "A mandatory field is missing or invalid.",
"details": {
"category": "return",
"timeframe": "ACH Operator: next file delivery after processing; an RDFI using it has the general 2 banking days after the settlement date of the original entry",
"timeframeKind": "banking-days",
"timeframeDays": 2,
"timeframeFrom": "original-settlement",
"account": "any",
"accountNote": null,
"writtenStatement": false,
"initiatedBy": "ACH Operator or RDFI",
"note": null,
"effectiveFrom": null,
"upcomingChange": null,
"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.
The deadline for a settlement date: GET /api/v1/ach/return-deadline?settlement_date=2026-11-25&code=R26 or the MCP tool ach_return_deadline.
Source: Nacha Operating Rules, Appendix Four (Return Entries). The code’s title is the Rules’ own; the rest is this site’s plain-language summary. It is informational and not a substitute for the Rules, your ACH Operator’s schedule or your ODFI agreement.