CO-197 — Prior authorization absent
The payer required prior authorization for this service and cannot find one attached to the claim.
Denial codes, and what to do about each one
A claim adjustment reason code tells you why a line was denied but not what to do next. These guides give the standard code description, the reasons it actually happens, the order to work it in, and the change that stops it recurring. Written for somebody with a denial open in front of them.
CO-16 — Claim lacks information or has a submission error
Something on the claim is missing or malformed. On its own the code tells you nothing — the detail is in the remark code that comes with it.
CO-29 — Time limit for filing has expired
The claim arrived after the payer’s filing deadline. This one is usually terminal, which is why it deserves attention before it happens rather than after.
CO-50 — Not deemed medically necessary
The payer does not accept that the documentation supports the service. This is a clinical argument, not a clerical one.
CO-45 — Charge exceeds the fee schedule
A contractual write-off rather than a denial. It only becomes a problem when the allowed amount is wrong.
CO-97 — Included in the payment for another service
The payer is bundling this code into another one on the same claim. Sometimes that is correct and sometimes it is not.
CO-18 — Exact duplicate claim or service
The payer already has this claim. Usually harmless, occasionally a sign that the original is stuck.
CO-22 — May be covered by another payer
The payer thinks somebody else is primary. Until coordination of benefits is corrected on their file, nothing on this claim will pay.
CO-27 — Expenses incurred after coverage terminated
The patient was not covered on the date of service.
CO-151 — Information does not support this many services
The payer accepts the service but not the quantity or the frequency at which it was billed.
CO-109 — Not covered by this payer or contractor
It went to the wrong place.
CO-B7 — Provider not certified or eligible on this date
A credentialing or enrollment problem rather than a claim problem: nothing this provider bills to this payer will pay until it is fixed, and it is rarely one claim.
CO-4 — Procedure code inconsistent with the modifier
The code and the modifier disagree, or a modifier the payer required was not there.
CO-11 — Diagnosis inconsistent with the procedure
The payer does not accept that the diagnosis submitted justifies the procedure performed.
CO-96 — Non-covered charges
The plan does not cover this service at all. Distinct from medical necessity, which is an argument about evidence.
CO-119 — Benefit maximum reached
The patient has used up what the plan allows for this benefit in this period.
CO-140 — Patient identification number and name do not match
The member ID and the name on the claim disagree with the payer’s record.
CO-170 — Payment denied for this provider type
The service may be covered, but not when delivered or billed by a provider of this type.
CO-234 — Procedure not paid separately
The payer treats this service as part of another one, similar to CO-97 but usually driven by the fee schedule rather than an NCCI edit.
CO-252 — Additional documentation required
The payer will not decide until it sees paperwork. Nothing happens until it arrives.
CO-198 — Prior authorization exceeded
An authorization exists. The problem is that you went past what it allowed — more units, more visits, or a longer date range than was approved.
CO-288 — Referral absent
The plan required a referral from the patient’s primary care physician and there is not one on file for this visit.
PR-204 — Not covered under the patient’s current plan
The service itself is excluded from this particular plan. This is a benefit design decision, not a coding error.
OA-23 — Prior payer’s adjudication
This is a coordination of benefits adjustment on a secondary claim. It reflects what the primary payer already did rather than a problem with your claim.
CO-185 — Rendering provider not eligible
The payer does not accept this provider as eligible for this service — an enrollment, credentialing or scope-of-practice problem rather than a coding one.
CO-8 — Procedure inconsistent with provider type
The payer does not expect a provider of this specialty to bill this code, based on the taxonomy attached to the claim.
CO-236 — Procedure/modifier combination not compatible
Two things billed on the same day conflict under NCCI edits or a state fee schedule. The pair is the problem, not either code alone.
CO-231 — Mutually exclusive procedures
The two procedures billed cannot clinically or by rule both have happened at the same encounter.
CO-107 — Related or qualifying claim not identified
This service only pays when it is linked to another one, and the link is missing from the claim.
PR-31 — Patient cannot be identified as our insured
The payer cannot match the patient to a member record. Usually a demographic or identifier mismatch rather than a coverage lapse.
CO-286 — Appeal time limits not met
The appeal arrived after the payer’s deadline. The clock for appealing is separate from, and usually shorter than, the clock for filing.
PR-1 — Deductible amount
The payer applied this amount to the patient’s deductible. It is not a denial — it is the plan working as designed, and the balance is the patient’s.
CO-5 — Procedure inconsistent with place of service
The code you billed is not one the payer accepts for the setting the service happened in.
CO-9 — Diagnosis inconsistent with patient age
The diagnosis code you sent is one the payer only accepts for a different age group.
CO-10 — Diagnosis inconsistent with patient gender
The diagnosis code is one the payer only accepts for a different gender marker than the one on the claim.
CO-15 — Authorization number missing or invalid
There is an authorization requirement here, and the number you sent is absent, wrong, or does not cover what was billed.
CO-24 — Charges covered under a capitation agreement
The payer says this service is included in a capitated arrangement, so there is no separate fee-for-service payment.
CO-32 — Patient is not an eligible dependent
The payer does not recognize this patient as a covered dependent on the subscriber’s policy.
CO-33 — Insured has no dependent coverage
The subscriber’s policy covers the subscriber only, so a dependent’s claim has nothing to pay against.
CO-35 — Lifetime benefit maximum reached
The policy has a lifetime cap on this benefit and the patient has used it.
CO-39 — Services denied at the time authorization was requested
The authorization was asked for and refused, and the service was delivered anyway.
CO-136 — Failure to follow the prior payer’s coverage rules
This is a secondary claim, and the secondary payer says the primary’s rules were not followed before it reached them.
CO-150 — Information does not support this level of service
The payer accepts the visit happened but not at the level you billed — usually an E/M downcode.
CO-167 — Diagnosis is not covered
The payer does not cover the condition you billed, whatever the procedure was.
CO-177 — Patient has not met eligibility requirements
There is coverage, but the patient has not satisfied a condition the plan attaches to it.
CO-181 — Procedure code invalid on the date of service
The code existed at some point but was not valid on the day the service happened.
CO-182 — Procedure modifier invalid on the date of service
The modifier attached to the code was not valid on the day of the service.
CO-183 — Referring provider not eligible to refer
Somebody is named as the referring provider who the payer will not accept in that role.
CO-184 — Ordering provider not eligible to order or prescribe
The provider named as ordering the service is not accepted by the payer in that role.
CO-226 — Requested information from the provider not supplied
The payer asked you for something, and either nothing arrived or what arrived did not answer the question.
CO-227 — Requested information from the patient not supplied
The payer asked the patient for something — very often about other insurance or an accident — and did not get it.
CO-242 — Services not provided by network providers
The plan pays only for its own network, and this provider was not in it for this service.
CO-251 — Attachment or documentation incomplete or deficient
Something was sent, and it did not contain what the payer needed.
CO-253 — Sequestration reduction in federal payment
A statutory percentage reduction applied to a federal payment. It is not a denial and there is nothing to appeal.
CO-256 — Service not payable under the managed care contract
The managed care contract in force does not provide for payment of this service.
CO-272 — Coverage or program guidelines not met
The service is covered in principle but this instance did not meet the programme’s conditions.
CO-B10 — Allowed amount reduced — a component of the procedure was already paid
The payer paid part of this procedure on another line or claim and has reduced this one to the difference, so the practice is not paid twice for the same work.
CO-273 — Coverage or program guidelines exceeded
The service is covered, but this instance went past a programme limit: more visits, units or sessions than the guideline allows.
N130 — Consult plan benefit documents for restrictions
The payer is pointing you at the plan document: there is a restriction on this service and the document says what it is.
N382 — Missing, incomplete or invalid patient identifier
The payer cannot match the patient from what was sent.
MA130 — Claim unprocessable — no appeal rights
The claim was rejected as unprocessable rather than denied. There is nothing to appeal — it has to be corrected and sent again as a new claim.
N29 — Missing documentation, orders, notes or report
The payer needs clinical documentation it does not have.
N30 — Patient ineligible for this service
The patient does not qualify for this particular service under their plan, even though they may hold coverage.
N34 — Incorrect claim form or format for this service
The service was billed on the wrong form or in the wrong format for the payer.
N54 — Claim inconsistent with the authorized services
There is an authorization, and what was billed does not match what it covers.
N115 — Decision based on a Local Coverage Determination
A published coverage policy for your region decided this, and that policy states exactly what would have been covered.
N122 — Add-on code cannot be billed by itself
The code billed only exists alongside a primary procedure, and no acceptable primary was on the claim.
N362 — Units of service exceed the payer’s maximum
The line carries more units than the payer allows for that code on one date, so it rejected the quantity rather than the service.
N381 — Adjusted per the contract — read the contract
An alert, not a denial: the payer processed the line under your contract and is pointing you at it. The reason code beside it carries the money.
N522 — Duplicate of a crossover claim
The secondary payer already has this claim — Medicare forwarded it automatically — and the copy you sent is the duplicate.
MA30 — Missing, incomplete or invalid type of bill
A facility claim problem: the three-digit type of bill in field 4 of the UB-04 does not fit the facility, the claim, or the frequency.
N830 — Processed under surprise-billing rules — the patient cannot be balance billed
An out-of-network service the payer processed under federal or state surprise-billing rules: the patient owes only the PR amount, and any dispute over the payment is with the payer, not the patient.
M115 — Denied — not a contract supplier for this item
A DMEPOS competitive bidding denial: for this item, in this area, Medicare pays only suppliers holding a contract, and this claim came from one that does not.
MA27 — Missing, incomplete or invalid Medicare number or name
Medicare cannot match the beneficiary: the Medicare Beneficiary Identifier or the name on the claim does not agree with the entitlement record.
M51 — Missing, incomplete or invalid procedure code
The code on the line is not one the payer recognises for that date: deleted, mistyped, or from the wrong code set.
N4 — Missing or invalid primary payer explanation of benefits
The secondary payer will not adjudicate without the primary payer’s decision: what was allowed, paid and adjusted, line by line.
N290 — Missing, incomplete or invalid rendering provider identifier
The NPI of the clinician who performed the service is missing from the claim, is not a valid NPI, or is not one the payer has linked to your group.
Questions
What is a claim adjustment reason code?
A CARC is the standard code a payer puts on a remittance to explain why a claim line was adjusted or denied. The code set is maintained by the X12 committee and is the same across payers, although the policy behind any individual denial is the payer’s own.
What is the difference between CO and PR?
The two-letter prefix is the group code. CO means contractual obligation, which you cannot bill to the patient. PR means patient responsibility, which you can. Billing a CO amount to a patient is a contract violation, so the prefix matters more than it looks.
Which denial costs practices the most?
CO-197, missing prior authorization, is in our experience the most common preventable one. CO-B7, a provider not eligible on the date of service, is the most expensive per occurrence because it is never one claim — it stops payment on everything that provider bills until the enrollment is corrected.
If this is work somebody on your team is doing at four in the afternoon, it can be a seat.
Next step
One seat. One month. Cancel any time.
Twenty minutes on a call is enough to tell whether this fits. If it does not, I will say so.
Or write to ops@softhomeglobal.com