FedACH is one of the two US ACH operators (the other is The Clearing House EPN). The wire format is the NACHA Operating Rules text file — a 94-character fixed-width record format with batch / company / entry / addenda records.
The NACHA format is *not* ISO 20022 today. There is a published ISO 20022 ↔ NACHA mapping (NACHA WEB / TEL / PPD ↔ pain.001 + pain.008) but the rail's native format remains NACHA's record-based text. US corporate treasurers integrating with their bank typically work in the NACHA format directly.
The US migration to ISO 20022 is incremental: Fedwire (the US wire rail) migrated to ISO 20022 in March 2025; FedACH has no concrete ISO 20022 cutover date.
iso-compliant treats US ACH as Phase-3 scope. The intermediate value (and the relevance to corporate treasury teams in the US) is the camt.053 ↔ NACHA Addenda mapping for inbound reconciliation, which is a clean fit with the existing camt.053 parser.