US · guidance
CMS Pub. 100-08, ch. 12, § 12.10.3
Insufficient Response to ADRs
If the documentation submitted is inadequate to support payment for the service/item
billed, or if the CERT review contractor could not conclude that the billed service/item
was provided, was provided at the level billed, and/or was medically necessary, the claim
is an insufficient documentation error with error code 21 assigned.
Error code 21 claims will be posted under the MAC feedback section of the C3HUB.
MACs should reach out to the provider or supplier to submit the requested
documentation to the CERT review contractor.
History
(Rev. 13678; Issued: 03-12-26; Effective: 04-13-26; Implementation: 04-13-26)
Provenance
- Source
- cms.gov
- Retrieved
- 2026-08-25
- Edition
- iom-2026-08-25
- Content hash
ceb1aaa38b00097252df2039e85a5840f09e752546540f01505184c8dca5495d
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