Medical Bill and Insurance Denial Code Decoder
Your Explanation of Benefits or bill is covered in codes like CO-45, 197, or PR-204. They decide how much you are told to pay, and many of them point to money you do not actually owe. Look yours up below.
Decode your denial code
Enter the code from your EOB or bill (for example CO-45, 197, or PR-204) to see what it means and whether you actually owe it. Nothing is saved.
First, read the two letters in front of the code
A CO amount is the provider’s write-off and is usually not your bill. A PR amount is yours, but can still be reduced.
Common codes
Charge exceeds the allowed or contracted amount
The provider billed more than your plan’s contracted or maximum allowable rate. Under an in-network contract, the provider accepts the allowed amount and writes off the difference.
What it means for you: If an in-network provider is billing you this difference, it is likely not yours to pay.
This is a contractual write-off. An in-network provider agreed to accept the plan’s rate, so this amount is usually not yours to pay. If it is on your bill, it can be disputed.
Have us dispute itDeductible amount
The amount applied to your plan deductible. You owe this until your deductible is met.
What it means for you: Confirm the deductible was applied correctly and that you have not already met it for the year.
This is cost-sharing you generally do owe. Verify it was applied correctly, then it can still come down through negotiation, a hardship discount, or financial assistance.
Have us lower itCoinsurance amount
Your percentage share of the allowed amount after the plan pays its part.
What it means for you: Check that the percentage matches your plan and was calculated on the in-network allowed amount.
This is cost-sharing you generally do owe. Verify it was applied correctly, then it can still come down through negotiation, a hardship discount, or financial assistance.
Have us lower itCopayment amount
The fixed copay for this visit or service under your plan.
What it means for you: Verify it matches the copay listed in your plan documents for this type of visit.
This is cost-sharing you generally do owe. Verify it was applied correctly, then it can still come down through negotiation, a hardship discount, or financial assistance.
Have us lower itPrior authorization or precertification was missing
The service was denied because required prior authorization, precertification, or notification was not obtained before care.
What it means for you: Frequently the provider’s responsibility, and often reversed with a retroactive authorization or a peer-to-peer review.
This kind of denial is commonly reversed. Often the insurer should still pay once records and the plan’s own rules are cited. You generally have 180 days to appeal.
Have us appeal itClaim lacks information or has a billing error
The claim is missing information or has a submission error, usually paired with a remark (N or M) code that names the specific problem.
What it means for you: Typically corrected and resubmitted by the provider, not a bill you should pay.
This is usually a correction or routing issue for the provider or payer to fix and resubmit, not an amount you should pay out of pocket.
Have us handle itNot deemed a medical necessity
The plan denied the service as not medically necessary under its criteria.
What it means for you: One of the most appealable denials, with a letter of medical necessity and records from your doctor.
This kind of denial is commonly reversed. Often the insurer should still pay once records and the plan’s own rules are cited. You generally have 180 days to appeal.
Have us appeal itNot covered under your current plan
The service, drug, or equipment is not a benefit under your current plan.
What it means for you: Verify the plan truly excludes it (worth appealing if not); otherwise it is a self-pay charge you can negotiate.
Non-covered can mean the plan wrongly excludes it (appeal) or that it is genuinely self-pay (negotiate). Both are workable once you confirm which it is.
Have us check itGroup prefixes can vary by payer, and one reason code can appear under more than one group, so your EOB’s own group code and wording are the final word. This tool is general information, not legal or insurance advice.
Why the code matters more than the dollar amount
When an insurer processes a claim, it attaches a standardized reason code to any amount it did not pay, plus a two-letter group code that says who is on the hook. That group code is the whole game. The same $800 can be a CO (Contractual Obligation) amount the provider agreed to write off, or a PR (Patient Responsibility) amount that is genuinely yours. Providers sometimes bill patients for CO amounts anyway, and most people just pay.
Reading the code tells you which of four situations you are in: an amount you should not have been billed, a denial worth appealing, a paperwork fix, or cost-sharing you owe but can still reduce. That is exactly what the tool above sorts out.
Not sure what the code is telling you?
Send us the Explanation of Benefits and the bill. CareRoute Bill Defense reads the codes, disputes contractual amounts you should not have been billed, appeals denials the insurer should have paid, and negotiates down whatever is genuinely yours.
Send us the EOBFree to submit. You only pay if we save you money.
Frequently asked questions
What are denial codes on my EOB or bill?
When an insurer processes a claim, it attaches standardized codes explaining any amount it did not pay. The main ones are Claim Adjustment Reason Codes (CARCs), like 45 or 197, and Remittance Advice Remark Codes (RARCs), like N130, which add detail. Each CARC comes with a group code (CO, PR, OA, or PI) that tells you who is responsible for the amount.
What is the difference between CO and PR codes?
It is the most important distinction on the whole document. CO (Contractual Obligation) means the provider agreed by contract to write the amount off, so it is usually NOT yours to pay, and if an in-network provider bills you for a CO amount, it can often be disputed. PR (Patient Responsibility) means the amount is genuinely yours: a deductible, coinsurance, copay, or a non-covered service. Two identical-looking dollar amounts can be treated completely differently depending on whether they are coded CO or PR.
Does a denial code mean I have to pay the bill?
Not necessarily. Many codes point to a provider write-off (CO amounts), a paperwork or routing fix the provider or payer needs to make, or an appealable denial where the insurer should still pay. Only PR-coded cost-sharing and genuine non-covered services are typically yours, and even those can often be reduced. The code tells you which situation you are in.
Which denial codes are worth appealing?
Denials for medical necessity (code 50), missing prior authorization (197), frequency or documentation (151), coverage-ended errors (27), and general "claim denied, see remark" codes (A1) are commonly overturned when you submit records and cite the plan’s own rules. You generally have 180 days to file an internal appeal, and an independent external review after that.
Can CareRoute handle the appeal or dispute for me?
Yes. CareRoute Bill Defense reads your EOB and denial codes, disputes contractual amounts you should not have been billed, appeals denials the insurer should have paid, and negotiates down any balance that is genuinely yours. It is free to submit, and you only pay if we save you money.
Related
Sources & references
This is general information, not legal, medical, or insurance advice, and does not create a client relationship. Denial and adjustment codes are standardized but their group prefix and meaning can vary by payer and claim, so your Explanation of Benefits and plan documents govern. Last updated: August 2026.