Medical Billing Denial Codes List: CARC and RARC Reference (2026)

Every electronic remittance advice (ERA) explains why a claim paid less than billed, or didn't pay at all, using standardized codes. Learn to read them fluently and denials stop being mysteries; they become work items with known fixes. This reference covers how the code system works, the codes you'll see most, and links to deep dives on the trickiest ones.

How Denial Codes Work: CARC, RARC, and Group Codes

Three pieces appear together on a remittance:

• Group code (2 letters): who is financially responsible for the adjusted amount.
• CARC (Claim Adjustment Reason Code): the reason the payment was adjusted. This is the number in "CO 45" or "PR 119."
• RARC (Remittance Advice Remark Code): extra detail, usually an N or M code like N290, that narrows down what exactly was wrong.

The four group codes

Group	Meaning	Who absorbs it
CO (Contractual Obligation)	Adjustment required by your payer contract	The practice writes it off; patient cannot be billed
PR (Patient Responsibility)	Deductible, coinsurance, copay, or non-covered benefit	Billable to the patient
OA (Other Adjustment)	Neither contractual nor patient responsibility	Depends on the reason code
PI (Payer Initiated Reduction)	Payer reduction not tied to contract	Often appealable

The group code matters as much as the number. CO 45 and PR 45 describe the same reason with completely different consequences for who pays.

The Most Common Denial Codes (and What They Mean)

Code	What it means	What to do
CO 16	Claim lacks information or has a submission error	Read the RARC, fix the missing data, resubmit. Not an appeal situation.
CO 18	Exact duplicate claim or service	Confirm whether the original paid; don't resubmit blindly.
CO 22	Care may be covered by another payer (coordination of benefits)	Verify primary coverage and rebill in the right order.
CO 29	Timely filing limit expired	Appeal only with proof of original timely submission.
CO 45	Charge exceeds the contracted fee schedule	Usually a routine contractual write-off; audit it for underpayments.
CO 50	Not medically necessary per the payer	Appeal with clinical documentation and LCD/NCD criteria.
CO 97	Bundled into another paid service	Check NCCI edits; add a modifier only if truly distinct.
CO 109	Wrong payer; claim belongs elsewhere	Identify the correct payer/contractor and submit there.
PR 119	Benefit maximum reached for the period	Verify the accumulator, then bill the patient or find secondary coverage.
CO 151	Frequency of services exceeds payer policy	Check frequency limits; appeal with necessity documentation if clinically justified.
CO 197	Missing prior authorization or precertification	Request retro-auth where allowed; otherwise appeal with cause.
CO 236	Procedure/modifier combination not compatible (NCCI)	Review the edit pair; correct coding or apply modifier 59/X if supported.
CO 253	Medicare sequestration reduction (2%)	Informational reduction; post it correctly, never bill the patient.
PR 1 / PR 2 / PR 3	Deductible / coinsurance / copay	Bill the patient; collect at point of service where possible.
PR 27	Coverage terminated before date of service	Verify eligibility; bill the patient or the correct active plan.
PR 204	Service not covered under the patient's plan	Confirm benefits; bill the patient with any required notices on file.

Reading a Denial in Three Steps

1. Group code first. CO means the practice absorbs it unless the adjustment itself is wrong. PR means the balance moves to the patient. PI is often worth a fight.
2. CARC second. That's the category of problem: eligibility, coding, authorization, filing, or contract math.
3. RARC third. The remark code usually names the exact missing or invalid element, especially on CO 16 denials.

Preventing Denials Beats Working Them

The industry average denial rate runs near 10% of claims; well-run billing operations keep it under 5%. The difference is front-end discipline: real-time eligibility checks, claim scrubbing against payer rules and NCCI edits before submission, authorization tracking, and a feedback loop that fixes root causes instead of re-fighting the same denial monthly. That workflow is exactly what our denial management service runs for practices, and what shows up as a rising clean claim rate.

Deep Dives on Specific Codes

• CO 45: charge exceeds fee schedule
• CO 16: claim lacks information
• CO 253: Medicare sequestration
• PR 119: benefit maximum reached
• CO 236: incompatible procedure/modifier combination
• The 10 most common denial codes overview

Drowning in denials your team doesn't have time to work? Our denial management team categorizes every denial by root cause, appeals what's winnable, and fixes the front-end process so the same code stops showing up. Get a free denial analysis.