EOB Denial Codes: What CO, PR & OA Mean

CO — Contractual Obligation

CO means the adjustment is a contractual obligation between the provider and the insurer. If the provider is in-network, you generally do NOT owe this amount — it's the difference between what the provider billed and the insurer's negotiated rate, and the provider agrees to write it off. Do not pay it just because it appears on the bill.

What to do: Confirm the provider is in-network, then treat the CO amount as a write-off. If the provider bills you for it anyway, call them citing the CO code and ask them to correct the bill. Federal and state balance-billing rules protect you in most in-network and many out-of-network emergency situations.

PR — Patient Responsibility

PR means the amount is your responsibility under your plan — a deductible, coinsurance, or copay, or a service your plan doesn't cover. PR amounts are what you actually owe after the insurer has applied your benefits. They are not errors in most cases, but a few PR codes (like PR-16) can hide a fixable problem.

What to do: Check the math: the PR amounts should match the deductible/coinsurance/copay in your plan documents. If a PR code is attached to a service you were told would be covered, appeal — you'll need the pre-authorization letter or the provider's documentation. Never pay a PR amount tied to a bill you haven't verified.

OA — Other Adjustment

OA means the adjustment doesn't fit cleanly into contractual or patient responsibility — often coordination of benefits (another payer should pay first), a payer error, or a non-claim payment. It is frequently the sign of a paperwork problem, not a bill you owe.

What to do: Start by checking whether another insurance plan is primary. If a second payer was supposed to process the claim, call your insurer and ask them to re-adjudicate with the correct ordering. If no other payer exists, request a corrected EOB — OA adjustments are often fixable without an appeal.

All denial codes explained