SFTP is the workhorse bank-channel transport outside the EBICS-dominant EU corridor. US, UK, and Asia-Pacific banks typically publish an SFTP endpoint, a corporate's public-key fingerprint is exchanged at onboarding, and the corporate uploads pain.001 batches to an inbox directory while the bank deposits camt.053 statements into an outbox directory.
The advantage over EBICS is universality — SFTP clients exist everywhere and require no specialist software. The disadvantage is the lack of a built-in signing model: each bank invents its own out-of-band signing scheme (PGP signatures on the file, or HSM-backed envelope signatures, or a separate API call to confirm submission).
iso-compliant produces the ISO 20022 XML that is then uploaded via SFTP. The customer's SFTP client and the per-bank signing scheme live outside iso-compliant's scope.