Medicare Denial vs. Adjustment: What's the Difference?

The Short Answer

• A denial means Medicare refused to pay for the service. You may be able to appeal.
• An adjustment means Medicare approved the claim but you owe a portion (like a deductible, coinsurance, or copay). This is standard cost-sharing and is not appealable.

The difference matters because it determines your next step. If it’s a denial, you have appeal rights. If it’s an adjustment, the question is whether the amount is correct.

The codes on your statement reflect this split. Each line item carries a Claim Adjustment Reason Code (CARC) maintained by X12; the two-letter prefix tells you which category it falls in. PR (“Patient Responsibility”) codes are adjustments — your share of an approved claim. CO (“Contractual Obligation”) codes are usually amounts the provider must absorb, not bill to you. OA (“Other Adjustment”) often shows the impact of another payer (Medicaid, a Medigap plan, an employer plan).

How To Tell the Difference

It’s a denial if your notice says:

• “Claim denied” or “not approved”
• “This service is not covered”
• “Not medically necessary”
• “The time limit for filing has expired”
• A specific reason Medicare refused to pay

It’s an adjustment if your notice shows:

• “Deductible amount” or “applied to your deductible”
• “Coinsurance” — your percentage share of the cost
• “Copay” or “copayment”
• Medicare paid a portion and you owe the rest

What To Do

If it’s a denial: Find your specific denial reason in our Denial Guide to understand what happened and whether to appeal.

If it’s an adjustment: Verify the amount is correct. Check that the deductible, coinsurance, or copay matches your plan’s terms. If you have supplemental insurance (Medigap, Medicaid, employer coverage), it may cover some or all of your share. See our Patient Responsibility section for more details.

If the bill doesn’t match your Medicare statement: Your provider may have sent you a bill before Medicare finished processing the claim. This is a timing issue. Participating Medicare providers must submit the claim to Medicare first and accept the Medicare-approved amount as full payment, so the provider’s bill should match what your Medicare Summary Notice (Original Medicare) or Explanation of Benefits (Medicare Advantage) shows you owe. Don’t pay the bill yet — wait for the MSN or EOB, compare the amounts, and call the provider’s billing office if they don’t match. This usually resolves in a single phone call. See our guide on Medigap crossover failures if your supplement didn’t pick up the remaining balance.

If you’re still not sure: Call 1-800-MEDICARE (1-800-633-4227) or contact your State Health Insurance Assistance Program (SHIP) for free help.

Sources

• Medicare.gov: Medicare Summary Notice (MSN) — what the MSN is, when it arrives, how it’s organized, and what a denied vs adjusted claim looks like on it.
• Medicare.gov: Checking the status of a claim — how to look up a Part A or Part B claim before the MSN arrives.
• Medicare.gov: Filing an appeal — what to do when the line item is a denial rather than an adjustment.
• X12: Claim Adjustment Reason Codes (CARCs) — official definitions for the CO / PR / OA group prefixes and the underlying numeric codes.

Frequently Asked Questions