How do I fix or resolve code CO-45?

Verify the payer's fee schedule or contracted rate for the billed CPT/HCPCS code and compare it to the allowed amount shown on the ERA to confirm the adjustment is correct. Check the provider contract or payer fee schedule to ensure the allowed amount matches the contracted rate; if it does not, request a contract review or file a payment dispute. If the adjustment is correct, post the contractual write-off in the practice management system — the patient cannot be balance billed for the difference (for in-network providers). If the provider is out-of-network and the plan allows balance billing, bill the patient for the difference per the plan's OON benefits. If multiple payers are involved, verify the adjustment does not duplicate prior payer contractual reductions and that COB is correctly applied.

CO-45Adjustment CodeContractual Obligation

Code CO-45

Problem Description

Charge exceeds fee schedule/maximum allowable or contracted/legislated fee arrangement. Usage: This adjustment amount cannot equal the total service or claim charge amount; and must not duplicate provider adjustment amounts (payments and contractual reductions) that have resulted from prior payer(s) adjudication. (Use only with Group Codes PR or CO depending upon liability)

Root Cause

The billed charge exceeds the fee schedule, maximum allowable amount, or contracted/legislated fee arrangement. This is a contractual adjustment, not a denial — the payer has adjudicated the claim and paid the contracted rate, and the difference between the billed amount and the allowed amount is written off under the provider's contract. This is standard for in-network providers with fee schedule contracts, Medicare (which pays based on the Medicare Physician Fee Schedule), and Medicaid. The adjustment amount cannot equal the total charge and must not duplicate prior payer adjustments.

Resolution Steps

1Verify the payer's fee schedule or contracted rate for the billed CPT/HCPCS code and compare it to the allowed amount shown on the ERA to confirm the adjustment is correct.
2Check the provider contract or payer fee schedule to ensure the allowed amount matches the contracted rate; if it does not, request a contract review or file a payment dispute.
3If the adjustment is correct, post the contractual write-off in the practice management system — the patient cannot be balance billed for the difference (for in-network providers).
4If the provider is out-of-network and the plan allows balance billing, bill the patient for the difference per the plan's OON benefits.
5If multiple payers are involved, verify the adjustment does not duplicate prior payer contractual reductions and that COB is correctly applied.

EHR Documentation Note

Claim adjusted CO-45 — charge exceeds fee schedule; verified contracted rate, posted contractual write-off, and confirmed no patient balance for in-network service.

Preventative Action

Maintain a current fee schedule for each payer in the practice management system and set charge amounts at or above the contracted rate to avoid under-billing; review fee schedules annually during contract renewals.

Related Codes in Contractual Obligation

CO-4

The procedure code is inconsistent with the modifier used. Usage: Refer to the 835 Healthcare Policy Identification Segment (loop 2110 Service Payment Information REF), if present.

CO-5

The procedure code/type of bill is inconsistent with the place of service. Usage: Refer to the 835 Healthcare Policy Identification Segment (loop 2110 Service Payment Information REF), if present.

CO-16

Claim/service lacks information or has submission/billing error(s). Usage: Do not use this code for claims attachment(s)/other documentation. At least one Remark Code must be provided (may be comprised of either the NCPDP Reject Reason Code, or Remittance Advice Remark Code that is not an ALERT.) Refer to the 835 Healthcare Policy Identification Segment (loop 2110 Service Payment Information REF), if present.

CO-18

Exact duplicate claim/service (Use only with Group Code OA except where state workers' compensation regulations requires CO)

This directory provides reference information only and does not constitute official legal, medical, or financial billing advice. Always consult the payer's official remittance advice and current coding guidelines.