ACH Standard Entry Class code
ATX SEC code: Financial EDI Acknowledgment
Zero-dollar acknowledgment of a CTX credit, sent by the RDFI.
What ATX is for
- An optional zero-dollar acknowledgment that a CTX credit was received, which can carry EDI addenda.
Sent back to the Originator of a CTX credit.
Debits, credits and addenda
Zero-dollar entries only.
Addenda on a forward entry: type 05, up to 9,999 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.
NOC codes and return codes have their own pages.
Common mix-ups
- ATX acknowledges a CTX credit; ACK acknowledges a CCD credit.
Where ATX 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 ATX 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 ATX from code or an AI agent
curl -s 'https://payopskit.com/api/v1/codes/ATX?set=ach-sec'{
"jsonrpc": "2.0",
"id": 1,
"method": "tools/call",
"params": {
"name": "lookup_payment_code",
"arguments": {
"code": "ATX",
"set": "ach-sec"
}
}
}{
"code": "ATX",
"set": "ach-sec",
"found": true,
"matches": [
{
"set": "ach-sec",
"code": "ATX",
"name": "Financial EDI Acknowledgment",
"description": "Zero-dollar acknowledgment of a CTX credit, sent by the RDFI.",
"details": {
"direction": "zero",
"addendaTypes": "05",
"minAddenda": 0,
"maxAddenda": 9999
}
}
]
}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.