CO-50 / PR-50

Denied as not medically necessary

The plan's reviewer decided the care wasn't needed, based on the records the plan had. This is the most common clinical denial, and it is decided on paperwork, so better paperwork can change it.

Official meaning (X12 code 50): These are non-covered services because this is not deemed a "medical necessity" by the payer.

Who pays

CO-50. Contractual obligation: the provider's contract with your plan makes this the provider's write-off. An in-network provider generally can't bill you for a CO amount.

PR-50. Patient responsibility: the plan says this part is yours to pay (deductible, copay, coinsurance, or a non-covered service).

What to do

Ask the plan for the clinical criteria it used and your claim file, free of charge.
Ask your doctor for a letter of medical necessity that answers those criteria point by point.
Appeal before the deadline, and ask for a reviewer in the same specialty.
If the plan says no again, request independent external review (private plans) or watch for the automatic independent review (Medicare Advantage).

If you appeal

These denials are decided on paperwork, so better paperwork can change them. Answer by showing the care meets the plan's own criteria: a letter of medical necessity from your doctor, the relevant chart notes, and what you already tried that didn't work. Ask the plan for the exact clinical criteria it used, and for a reviewer in the same specialty.

What the appeal asks for: Overturn the medical-necessity denial. Please provide, free of charge, the clinical criteria, guidelines and reviewer credentials relied on, and have the appeal reviewed by a physician in the same or a similar specialty who was not involved in the initial decision.

Basis: 29 CFR §2560.503-1(h)(2)(iii) and (h)(3)(iii)

Deadlines for the first appeal

employer plan: 180 days from the notice
ACA Marketplace plan: 180 days from the notice
Medicare Advantage plan: 65 days from the notice
Original Medicare: 120 days from the notice
Medicaid: 60 days from the notice

The date printed on your notice controls. Urgent care can be appealed on an expedited (72-hour) basis.

What the data show

11.5%Only 11.5% of denied Medicare Advantage prior authorization requests were appealed in 2024. KFF, 2024 data

80.7%80.7% of appealed Medicare Advantage prior authorization denials were partially or fully overturned in 2024. KFF, 2024 data

<1% (262,982 appeals)Fewer than 1% of denied in-network marketplace claims were appealed in 2024 (at least 262,982 appeals). KFF, 2024 data

66% upheldInsurers upheld 66% of denials on internal appeal in 2024 (165,863 denials). KFF, 2024 data

5%Only 5% of in-network marketplace denials were based on medical necessity. KFF, 2024 data

Averages across all denials; not a prediction for yours.

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General information, not legal or medical advice. Owed is a document-preparation and sending service, not a law firm.