CARC 50: Not medically necessary

Group code context

Often sent with group code CO, which means you cannot bill the patient unless they signed a valid advance notice (for Medicare, an ABN) before the service.

Common causes

• Diagnosis code does not support the service under the payer's policy
• Service done more often than the policy allows
• Documentation does not show why the service was needed

Step-by-step fix

1. Read the payer's coverage policy (for Medicare, the LCD or NCD)
2. Check the diagnosis codes on the claim
3. If a more specific supported diagnosis was documented, correct the claim
4. If the claim was correct, appeal with the notes

Appeal guidance

Appeal with clinical notes that show why the service was needed, and quote the payer's own policy.

When not to appeal

Do not appeal if the documentation does not support the service. Use it to improve documentation instead.

Prevention checklist

• Check coverage policies for high-cost services before scheduling
• Get an ABN signed when Medicare may not cover a service
• Use prior authorization where the payer offers it

Related codes

CARC 96: Non-covered charge

CARC 197: Prior authorization missing

Source and review

Last checked: 2026-10-05