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CO-88 Denial Code (Deactivated): Prior Overpayment Offset

CO-88 meant the adjustment was the payer collecting money it had overpaid on an earlier claim, taken from this payment. X12 deactivated it without naming a successor; offsets are now generally reported as provider-level adjustments on the 835.

X12 deactivated CARC88 on June 30, 2007. Payers should no longer use it on new remittances, but it can still appear on older ERAs, corrected claims, and appeals.

Code: CO-88 (CARC 88)
Status: Deactivated StoppedJune 30, 2007 (in use since January 1, 1995).
Code set: Claim Adjustment Reason Codes (CARC)
Group codes: CO (Contractual Obligation): The offset reduced the provider's payment; it had nothing to do with the patient's balance.
Official description: Adjustment amount represents collection against receivable created in prior overpayment.
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified: September 24, 2026 against the official X12 list.

What CO-88 meant

When a payer determines it paid too much on a past claim, it sets up a receivable against the provider. Rather than asking for a refund check, many payers simply withhold that amount from future payments. CARC 88 labeled the portion of a payment that was being kept to satisfy that earlier overpayment.

What replaced it

X12 did not name a replacement. On current remittances, recoupments are usually reported as provider-level adjustments rather than inside an individual claim’s adjustments, which keeps the new claim’s accounting clean. Active claim-level codes that often relate to the original overpayment include CO-B13, CO-129, and CO-195.

If you still see CO-88

It can surface in older payment histories. The key task is to tie the withheld amount back to the claim that was overpaid. Apply the payment to the current claim in full, then record the offset against the older claim’s credit balance, so neither account is misstated.

If you do not recognize the overpayment, ask the payer for the original claim number and the reason it was considered overpaid, and dispute it if you disagree.

CO-B13 (Previously paid.): Previously paid; payment for this claim may have been made in an earlier remittance.
CO-129 (Prior processing information appears incorrect.): Prior processing information appears incorrect.
CO-195 (Refund issued to an erroneous priority payer for this claim/service.): Refund issued to an erroneous priority payer for this claim or service.

CO-88 FAQ

Does a CO-88 mean this claim was underpaid?

Not exactly. The claim may have been paid correctly, but part of the money was kept to settle an overpayment on a different claim. Your ledger needs to reflect both transactions.

How do recoupments show on remittances now?

Typically as provider-level adjustments in the 835's PLB segment, often with a reference to the original claim, rather than as a claim adjustment reason code.

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