Billing

Denial and remittance codes

Last reviewed November 3, 2026 · Educational use only

Every adjustment on a remittance carries a group code (who is responsible) and a claim adjustment reason code (why). Remittance advice remark codes add detail. Search the common ones below.

Group codes

Code	Name	Who owes it
`CO`	Contractual obligation	Provider writes it off. Cannot be billed to the patient.
`PR`	Patient responsibility	Patient (deductible, coinsurance, copay, non-covered with notice).
`OA`	Other adjustment	Neither; usually coordination of benefits or informational.
`PI`	Payer-initiated reduction	Provider, per the payer; not billable to the patient.
`CR`	Correction or reversal	Adjusts a prior claim.

Claim adjustment reason codes (CARC)

Filter by code or words

CARC	Meaning	Typical group	What to do	For the patient
`1`	Deductible amount	`PR`	Bill the patient; confirm the amount against the accumulator.	This went to your deductible. You owe it to the provider.
`2`	Coinsurance amount	`PR`	Bill the patient.	Your coinsurance share.
`3`	Co-payment amount	`PR`	Collect if not already collected at the visit.	Your copay.
`4`	Procedure code inconsistent with the modifier, or a required modifier is missing	`CO`	Fix the modifier and send a corrected claim.	A billing error; ask the provider to correct it. You should not owe it.
`5`	Procedure code or bill type inconsistent with the place of service	`CO`	Check the place of service code and resubmit.	A billing error to be corrected.
`11`	Diagnosis inconsistent with the procedure	`CO`	Review coding and documentation; correct or appeal.	Coding issue; ask the provider to review.
`16`	Claim lacks information or has submission/billing errors	`CO`	Read the RARC for the missing item, fix and resubmit.	Paperwork problem; usually fixed by the provider.
`18`	Exact duplicate claim or service	`CO`	Check status of the original; send a corrected claim (frequency 7) instead of a duplicate.	Duplicate submission; you should not be billed twice.
`22`	May be covered by another payer per coordination of benefits	`CO/OA`	Get updated COB from the patient; bill the primary first.	Your insurer thinks you have other coverage. Call them to update it.
`23`	Impact of prior payer(s) adjudication	`OA`	Informational on secondary claims; post accordingly.	Your other plan's payment was taken into account.
`26`	Expenses incurred before coverage	`PR/CO`	Verify the effective date; bill the correct plan or the patient.	Service was before your coverage started.
`27`	Expenses incurred after coverage terminated	`PR/CO`	Find current coverage; bill the correct payer.	Coverage had ended. Check for new coverage.
`29`	Time limit for filing has expired	`CO`	Write off unless you have proof of timely filing; appeal with 999/277CA proof.	Late filing by the provider; generally not billable to you in network.
`31`	Patient cannot be identified as our insured	`CO`	Check member ID, name and date of birth against the card.	Your details didn't match; give the provider your current card.
`45`	Charge exceeds fee schedule / maximum allowable or contracted amount	`CO`	Contractual write-off. Do not bill the patient.	The network discount. You do not owe it.
`50`	Not deemed a medical necessity by the payer	`CO/PR`	Appeal with records and policy criteria; patient liable only with proper advance notice.	Your plan said it wasn't necessary. You can appeal.
`96`	Non-covered charge(s)	`PR/CO`	Check the RARC; bill the patient only if excluded and they were informed.	Not covered by your plan. Ask whether you were told in advance.
`97`	Payment included in the allowance for another service (bundled)	`CO`	Check NCCI edits; appeal or add a valid modifier if distinct.	Included in another charge; you should not pay it separately.
`109`	Claim not covered by this payer; send to the correct payer	`CO`	Find the right payer (Medicare Advantage, Medicaid MCO, other plan).	The wrong insurer was billed.
`119`	Benefit maximum for this time period or occurrence reached	`PR`	Verify the limit; bill the patient or appeal for an exception.	You used up this benefit's limit for the period.
`151`	Information doesn't support this many or this frequency of services	`CO`	Appeal with documentation of need.	Frequency limit; your provider can appeal.
`167`	Diagnosis is not covered	`CO/PR`	Review coding and policy; appeal if appropriate.	Plan does not cover services for this diagnosis.
`170`	Payment denied when performed or billed by this type of provider	`CO`	Check the payer's provider-type rules and taxonomy.	Plan requires a different type of provider.
`197`	Precertification / authorization / notification absent	`CO`	Retro-authorization request or appeal; usually the provider's liability in network.	Approval wasn't obtained. In network, you generally aren't responsible.
`204`	Service not covered under the patient's current benefit plan	`PR`	Bill the patient if properly informed; check for other coverage.	Your plan doesn't include this service.
`242`	Services not provided by network / primary care providers	`CO/PR`	Check network status, referral or gap exception; appeal if a gap exception applies.	Out of network or no referral.
`253`	Sequestration: reduction in federal payment	`CO`	Expected 2% Medicare reduction; write off.	A federal adjustment. You don't owe it.

Paraphrased from the X12 code list, which is updated several times a year. Confirm the official wording at x12.org before relying on it.

Reading a denial

Look at the group code first. CO means the patient owes nothing for that amount; PR means they do.
Separate fixable from final. Missing information (16), coding mismatches (4, 11), COB (22) and duplicates (18) are fixed by correcting and resubmitting. Medical necessity (50), authorization (197) and non-covered (96, 204) usually need an appeal or a patient conversation.
Read the RARC. The remark code (for example N290 missing rendering provider identifier, M127 missing patient medical record) often names the exact problem.
Correct vs appeal. A corrected claim (frequency code 7 replacement, 8 void) fixes your data. An appeal disputes the payer's decision. Sending the wrong one wastes the filing window.
Track by root cause. Group denials by code each month to find the front-desk, coding or authorization step that needs fixing.