Claim adjustment reason code
CO-256: Service not payable under the managed care contract
CO-256 means: Service not payable per managed care contract. The managed care contract in force does not provide for payment of this service.
Read the group code before you act on this
256 is the claim adjustment reason code. The CO in front of it is the group code — a separate field the payer sets on the remittance. The same reason code arrives under different group codes depending on the payer and the situation, and the group code, not the reason code, decides who owes the money.
- CO — contractual obligation. You write it off. You may not bill the patient.
- PR — patient responsibility. Billable to the patient.
- OA — other adjustment, and PI — payer initiated reduction. Neither is patient responsibility.
What causes it
- Service excluded from the contract’s covered list
- Service carved out to a different vendor — behavioural health, vision, laboratory and radiology are the usual carve-outs
- Contract requires the service to be delivered by a designated provider
- Billed to the plan when the capitated group holds the risk
How to work it
- Read the contract’s covered services and carve-outs before appealing. Most of these are correct denials sent to the wrong entity.
- Where the service is carved out, bill the carve-out vendor inside its own filing window.
- Where the contract does cover it, appeal with the contract language cited specifically.
- Read the group code before any balance is moved to the patient.
How to stop it recurring
Keep a per-contract summary of carve-outs where billing can see it. Carve-outs are invisible on an eligibility check and are the usual reason for this denial.
Who does this work
A ar calling & denial management seat at $1,700 per seat per month works this queue full time, during your business hours, inside your own system. Every call is logged with the payer reference number and the outcome, and every Friday you get it in writing.
Codes worked the same way
CO-256 is checked against the contract before any work is done. So are these, which is why a queue sorted by recovery route moves faster than one sorted by code number — the same person, in the same system, with the same evidence to hand, clears all of them in one pass.
- CO-45 — Charge exceeds the fee schedule
- CO-97 — Payment included in another service
- CO-18 — Exact duplicate claim or service
- CO-288 — Referral absent
- PR-204 — Not covered by this plan
- OA-23 — Prior payer already adjudicated
Specialties that name this among their costliest
These are specialties whose own worst denials include one of this kind. The line under each is the denial they name, quoted from their page so you can see what the link is based on.
- AnesthesiaPost-op pain blocks bundled into the anesthesia claim
- OphthalmologyRetinal imaging and fundus photography done at the same visit, with one line denied as bundled because the record never gives a separate reason for each test.
- OtolaryngologyThe operative note does not state which sinuses were entered on which side, so the sinus surgery lines are bundled together or only one side is allowed.
- Urgent CareA global urgent care case rate billed alongside a separate evaluation and management line where the contract pays one or the other, and the second line drops off
- Primary CareA preventive visit and a same-day problem visit written up in one undivided note, so the problem visit bundles into the wellness visit and is not paid separately.
- OncologyPayer required the drug through its contracted specialty pharmacy, the practice infused from its own stock, and the buy-and-bill claim was denied in full.
What leaving it costs
Working a denied claim costs $57.23 per denied claim in administrative time. Source. At 100 denials a month — an illustration, not a measurement of your practice — that is $5,723 a month, or $68,676 a year, in labour alone.
The figure that makes it worth spending: about 90% of initially denied claims are eventually paid. Source. The reason a denial sits is almost never that nobody knows how to work it — it is that nobody has the hours.
Questions
What does denial code CO-256 mean?
Service not payable per managed care contract. In plain terms: The managed care contract in force does not provide for payment of this service.
What causes CO-256?
Service excluded from the contract’s covered list. Service carved out to a different vendor — behavioural health, vision, laboratory and radiology are the usual carve-outs. Contract requires the service to be delivered by a designated provider. Billed to the plan when the capitated group holds the risk.
How do you fix a CO-256 denial?
Read the contract’s covered services and carve-outs before appealing. Most of these are correct denials sent to the wrong entity.. Where the service is carved out, bill the carve-out vendor inside its own filing window.. Where the contract does cover it, appeal with the contract language cited specifically.. Read the group code before any balance is moved to the patient..
Can CO-256 be prevented?
Keep a per-contract summary of carve-outs where billing can see it. Carve-outs are invisible on an eligibility check and are the usual reason for this denial.
Is CO-256 the same as PR-256?
Same reason, different group code. The number 256 is the reason: The managed care contract in force does not provide for payment of this service. The prefix says who carries the amount. CO means contractual obligation — the payer says the amount is not billable to anybody, and it is written off unless the denial itself is overturned. PR-256 is the same reason assigned to patient responsibility — the payer says the amount is owed by the patient, and it is billed to them. Read the prefix before the number: it decides whether you appeal, write off, or bill the patient.
What about the codes next to CO-256?
CO-255 and CO-257 are separate codes and this site does not yet cover them. The authoritative list is the X12 Claim Adjustment Reason Codes at x12.org/codes/claim-adjustment-reason-codes; a code is only described here once its official text, causes and fix have been written and checked.
Code descriptions are the standard X12 claim adjustment reason and remittance advice remark code text. Payer policies differ, and the payer’s own coverage policy governs any individual claim. This page is working guidance, not legal or clinical advice.
Last updated 2026-09-12. This is operational guidance drawn from payer remittance practice, not legal, coding or reimbursement advice. Payer-specific rules vary and change; confirm against the payer’s own policy before acting on a specific claim.
Other denial codes
- CO-24 — Charges covered under a capitation agreement
- CO-109 — Not covered by this payer or contractor
- CO-170 — Payment denied for this provider type
- CO-96 — Non-covered charges
- CO-288 — Referral absent
- N830 — Processed under surprise-billing rules — the patient cannot be balance billed
- How to find payer underpayments nobody is looking for
- The prior authorization checklist that prevents CO-197
- How to overturn a timely filing denial
Next step
Somebody to work your CO-256 queue
Full time, US hours, inside your system. Twenty minutes on a call is enough to tell whether it pays for itself.
Or write to ops@softhomeglobal.com

