Attach clinical documentation to a claim using the X12 275 additional information transaction

Verified steps

1. Identify the attachment trigger: either a payer-initiated additional information request (received as a 277 with status code requiring attachment) or a provider-initiated attachment linked to a prior authorization or claim
2. Build the 275 transaction (005010X210): ISA/GS envelope, ST*275, BGN segment with purpose code '11' (original) or '15' (re-submission), Loop 2000A submitter loop, Loop 2000B subscriber loop, Loop 2000C patient loop if different
3. In Loop 2100 include the claim reference: REF*EJ (patient account number) and REF*F8 (original reference number from the payer's request) to link the attachment to the specific claim or request
4. Attach the clinical content in CAT and EFI or BIN segments: CAT segment identifies the attachment type (e.g., CAT01 for report type code), EFI segment carries the attachment control number, and BIN or BDS segments carry the binary or base64-encoded document data (e.g., PDF, CDA)
5. If using a PWK-based attachment workflow on the 837 side, the PWK segment on the claim references an attachment control number; submit the 275 with the matching control number so the payer can join them
6. Submit the 275 through your clearinghouse or directly to the payer attachment portal; retain the submission timestamp and any acknowledgment for audit