999 — Functional Acknowledgment

The 999 transaction is a functional acknowledgment that confirms whether an X12 transmission was syntactically valid. It is returned by the receiver (payer or clearinghouse) after processing the envelope of a submitted transaction (e.g., 837P).

The parse-x12 activity supports parsing 999 files. Handling of 999 responses (e.g., flagging rejected transmissions) is typically implemented as a project-specific activity.