Comparison · Billing

CO-50 vs CO-97 (denial reason)

CO-50 means the service is not deemed a medical necessity by the payer. CO-97 means the benefit is included in the payment for another service already adjudicated.

Last reviewed May 24, 2026

Side by side

Option A

CO-50 (Not medically necessary)

These are non-covered services because this is not deemed a medical necessity by the payer.

CARC 50

CARC 50 (Contractual Obligation).
Often tied to an LCD/NCD coverage decision.
Patient cannot be billed unless an ABN was executed.

Option B

CO-97 (Bundled — payment included)

The benefit for this service is included in the payment/allowance for another service/procedure that has already been adjudicated.

CARC 97

CARC 97.
Usually traces to an NCCI bundling edit.
Often resolved by appending the correct modifier (XE/XP/XS/XU/59/25).

What the payer is saying

CO-50We do not cover this for this diagnosis

CO-97We already paid for it inside another code

Where to look first

CO-50Payer LCD/NCD or medical policy

CO-97NCCI Procedure-to-Procedure edit table

Typical resolution path

CO-50Diagnosis correction, ABN check, or medical-necessity appeal with chart

CO-97Verify NCCI edit and append the correct distinction modifier; resubmit

Can patient be billed

CO-50Only if an advance beneficiary notice (ABN) was executed

CO-97No — it is a payer contractual write-off when no modifier overrides apply

When to use CO-50 (Not medically necessary)

Recognizing CO-50 on a remit: pull the LCD/NCD; if the diagnosis is wrong, correct and resubmit; if not, appeal with clinical documentation.

When to use CO-97 (Bundled — payment included)

Recognizing CO-97 on a remit: pull the NCCI edit; if a distinction modifier applies (separate site, session, etc.), append and resubmit.

Common mistakes

Appending modifier 59 to every CO-97 reflexively without confirming the underlying NCCI logic.
Billing the patient for a CO-50 without an executed ABN.
Treating CO-50 as a coding error rather than a coverage decision.

Sources

X12 — Claim Adjustment Reason Codes (CARC)https://x12.org/codes/claim-adjustment-reason-codes
CMS — NCCI Editshttps://www.cms.gov/medicare/coding-billing/national-correct-coding-initiative-ncci-edits
CMS — Advance Beneficiary Notice (ABN)https://www.cms.gov/medicare/medicare-general-information/bni

More Billing comparisons

Glossary

Guides

medicare denial codes

Take it into the workspace

Diagnose CO-50 vs CO-97 in the Denial Workbench

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Authored by D3rx

D3rx is a healthcare-billing and compliance research aid maintained by D3rx Inc. Articles are drafted by an LLM (Anthropic Claude) against primary HHS, OCR, CMS, eCFR, NIST, and state-regulator publications, and reviewed for restraint and source fidelity by the D3rx team.

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This comparison is a research aid for billing and compliance staff. It does not provide legal, medical, or financial advice and does not replace counsel. References cited link to primary sources at CMS, HHS, OCR, eCFR, NIST, and the relevant payer or state regulator. Last reviewed May 24, 2026.