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CO-131 Denial Code: Claim-Specific Negotiated Discount

CO-131 means the payment was reduced by a claim-specific negotiated discount. Instead of a standard fee schedule, the reduction reflects a discount agreed for this particular claim, for example through a single-case agreement or a repricing negotiation.

Code: CO-131 (CARC 131)
Status: Active In use since February 28, 1997.
Code set: Claim Adjustment Reason Codes (CARC)
Group codes: CO (Contractual Obligation): The discount is a provider write-off under the negotiated agreement. It cannot be billed to the patient.
Official description: Claim specific negotiated discount.
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified: September 24, 2026 against the official X12 list.

What CO-131 means

CARC 131 is a claim specific negotiated discount. The payer reduced your charge based on a discount agreed for this particular claim, not a general fee schedule. It shows up most often on out-of-network claims that were negotiated one at a time, on single-case agreements, and on claims handled by repricing vendors.

In many cases it is correct: you or your billing team agreed to accept a certain amount, and the payer is honoring it. It becomes a problem when the discount does not match what was agreed, or when no agreement exists.

Example: an out-of-network provider agrees to a single-case rate for a complex procedure. The claim pays at that rate, and the difference from the billed charge appears as CO-131.

Common causes

A single-case agreement or letter of agreement for an out-of-network patient.
A repricing vendor negotiated the claim on the payer’s behalf, sometimes by phone or email offer.
A rental network agreement the payer believes applies to you.
A settlement on a disputed claim, such as through a negotiation period.
The payer applied a discount from a different claim or a different agreement by mistake.

How to fix it

Match the discount to the agreement. Pull the signed agreement or the negotiation record and compare the rate.
If it matches, post CO-131 as a contractual adjustment and close the claim.
If it does not match, contact the payer or repricing vendor with the agreement and request reprocessing.
If you never agreed, dispute it in writing. Ask the payer to identify the agreement and the signer. Follow the payer’s appeal process and any applicable federal or state dispute process for out-of-network claims.
Recheck the patient’s share. Make sure cost-sharing is calculated on the agreed amount and do not bill the patient for the discount.

How to prevent it

Put every single-case agreement in writing, with the rate, services, dates, and claim references.
Keep a log of repricing offers and who accepted them.
Review rental network participation so you know which networks can access your rates.
Compare paid amounts against agreements with an ERA Analyzer to catch discounts that were applied incorrectly.
For more on separating pricing adjustments from denials, see how to read CARC and RARC codes.

CO-45 (Charge exceeds fee schedule/maximum allowable or contracted/legislated fee arrangement.): Standard fee schedule or contracted rate reduction, used when there is no claim-specific deal.
CO-103 (Provider promotional discount (e.g., Senior citizen discount).): A promotional discount offered by the provider rather than negotiated with the payer.
CO-44 (Prompt-pay discount.): Prompt-pay discount tied to payment timing.
CO-P24 (Payment adjusted based on Preferred Provider Organization (PPO).): Payment adjusted based on a PPO network agreement, used in property and casualty claims.

CO-131 FAQ

When would I see CO-131 instead of CO-45?

When the reduction comes from a deal made for this specific claim, such as a single-case agreement for an out-of-network patient or a negotiation by a repricing vendor, rather than your standing fee schedule.

What if I never agreed to a discount?

Ask the payer for the agreement it applied. Out-of-network claims are sometimes repriced by vendors that claim a network agreement; if you did not agree, dispute the reduction.

Can the patient be billed for the discount?

No. Under CO the negotiated discount is a write-off. Balance-billing rules and your agreement may also limit what the patient owes.

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