CO-45: Charge Exceeds Fee Schedule / Maximum Allowable

What Does CO-45 Mean?

When CARC 45 is paired with Group Code CO, the adjustment represents a contractual obligation between your practice and the payer. Your practice agreed to accept the payer's allowed amount as full payment for the service under your participating provider agreement. The difference between your billed charge and the allowed amount must be written off. You are contractually prohibited from billing the patient for this adjustment amount, making it entirely the provider's financial responsibility.

When CARC 45 appears on a remittance advice, it signals that the amount your practice billed for a service was higher than what the payer has established as the allowable payment under their fee schedule, negotiated contract, or a legislated rate cap. This is one of the most frequently encountered adjustment codes in medical billing and is typically a standard part of the claims adjudication process rather than a true denial. The payer is telling you that the difference between your billed charge and their allowed amount has been adjusted off.

The root cause is almost always a gap between what your charge master lists and what the payer will actually reimburse. This gap can stem from several scenarios: your internal fee schedule may not have been updated after a payer released new rates, your billed CPT or HCPCS codes may not align with the documentation on file, or the service may be subject to a statutory fee cap that limits what can be charged regardless of contract terms. For out-of-network providers, the adjustment reflects the difference between billed charges and the payer's usual, customary, and reasonable (UCR) rate.

Understanding CARC 45 requires looking at the accompanying group code. The group code determines who absorbs the financial impact of the adjustment. A CO (Contractual Obligation) pairing means your practice must write off the difference and cannot balance bill the patient. A PR (Patient Responsibility) pairing shifts that difference to the patient. The distinction is critical for accurate posting, patient billing, and compliance with payer contracts.

Common Causes

How to Resolve

Verify the adjustment against your payer contract and fee schedule, then either write off the amount or appeal if the payer applied rates incorrectly.

1. Verify the allowed amount matches your contract Compare the payer's allowed amount against your contracted rate for the billed procedure code. If the allowed amount matches, post the CO-45 adjustment as a contractual write-off in your practice management system.
2. Confirm patient is not billed for the write-off Audit your posting workflow to ensure the CO-45 amount is hitting the contractual adjustment bucket, not patient responsibility. Billing patients for CO-adjusted amounts violates your participation agreement and can trigger compliance issues.
3. Appeal only for rate discrepancies If the allowed amount does not match your contract, gather your signed agreement and the payer's published fee schedule as supporting documentation. Contact your payer representative or submit a formal appeal showing the contracted rate versus the applied rate.

Common RARC Pairings

The RARC code tells you exactly what triggered the CO-45:

How to Prevent CO-45

• Keep your charge master aligned with payer fee schedules so that CO-45 adjustments are expected and budgeted rather than surprises that distort revenue projections
• Reconcile contracted rates annually during renewal periods and flag any payer-initiated rate changes immediately in your billing system
• Set up automated alerts in your practice management system to flag when CO-45 adjustment amounts exceed a threshold percentage of the billed charge, which may indicate a contract loading error

General Prevention

• Regularly audit fee schedules against charges and update billing systems when payers release fee schedule changes
• Verify payer contract terms thoroughly before billing and charge only contracted amounts
• Implement revenue cycle software with built-in fee schedule validation and claim scrubbing
• Train billing staff on coding guidelines and proper modifier usage
• Subscribe to CMS fee schedule alerts and monitor payer communications for rate changes
• Negotiate clearer rate alignments during contract renewals
• Verify patient eligibility and benefits before providing services
• Use clearinghouse claim scrubbing services to flag potential CO-45 issues before submission

Also Filed As

The same CARC 45 may appear with different Group Codes:

Related Denial Codes