CARC 50, 109, 29 — Medical necessity, wrong payer, timely filing

Three high-volume denial CARCs: 50, 109, and 29#

CARC 50 — "These are non-covered services because this is not deemed a 'medical necessity' by the payer." The payer determined the service was not medically necessary for the reported diagnosis. This is a clinical denial. Resolution: verify the diagnosis-to-procedure linkage and the payer's medical-necessity / Local Coverage Determination (LCD) or National Coverage Determination (NCD) policy. If the documentation supports necessity, file an appeal with the clinical notes, the supporting diagnosis, and the relevant coverage policy. If a covered diagnosis was simply omitted from the claim, submit a corrected claim. An Advance Beneficiary Notice (ABN) may shift liability to a Medicare patient when issued correctly before service.

CARC 109 — "Claim/service not covered by this payer/contractor. You must send the claim/service to the correct payer/contractor." This is a coordination-of-benefits / wrong-payer problem: the claim went to a payer that is not responsible (e.g., the patient changed plans, a different plan is primary, or the service belongs to a carved-out vendor). Resolution: verify current eligibility and the correct primary payer, then submit the claim to the right payer. No appeal to the wrong payer will succeed; the fix is rerouting. This is why real-time eligibility verification at the front end prevents 109 denials.

CARC 29 — "The time limit for filing has expired." A timely-filing denial: the claim arrived after the payer's filing deadline (commonly 90–365 days from date of service, varying by payer). Group code is usually CO-29, so it is not billable to the patient. Resolution: appeal with proof of timely filing — clearinghouse acceptance reports, original submission date stamps, or evidence the delay was caused by the payer (e.g., a prior wrong-payer denial that reset the clock). Without proof, timely-filing denials are usually upheld, which is why submission and follow-up cadence matters so much in revenue cycle management.