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Can I bill the patient for the CO-45 write-off?

No. CO-45 is a contractual adjustment for in-network providers. The patient cannot be billed for the difference between billed charges and the contracted rate. Billing patients for contractual write-offs is balance billing and violates most provider contracts.

What should I do if the allowed amount is lower than my contracted rate?

File a formal appeal with your signed contract and current fee schedule as documentation. Clearly identify the CPT code, the contracted rate, the allowed amount on the EOB, and the difference owed. Payers sometimes apply outdated fee schedules or incorrect fee schedule years.

No. CO-45 is a contractual adjustment, not a denial. The claim is still paid — it is adjusted to the contracted rate. The claim is not denied or rejected; it is processed at the contracted amount.

What if my provider was processed as out-of-network but should be in-network?

File a corrected claim with proof of credentialing, your participation agreement, and the effective date of your network status. If denied, escalate to your provider relations representative. This is a common issue during contract renewals or when new NPIs are added.

Why is my CO-45 adjustment higher than expected?

Possible causes: multiple procedure reductions, bilateral adjustments, fee schedule updates, or incorrect processing. Review the EOB carefully for additional remark codes and cross-reference the allowed amount against your contracted rate for that CPT code.

Home Payer Denial Intelligence CO-45Medicare

CO-45Medicare

How to Work CO-45 for Medicare

Master Denial Codes CO-45 Overview

Quick Answer

CO-45 (Charge Exceeds Fee Schedule): Charge exceeds fee schedule / maximum allowable or contracted/legislated fee arrangement. (Use code 45 to show the dollar amount.) Read the accompanying RARC codes on the ERA/EOB to identify the specific missing or incorrect information, then correct and resubmit as a corrected claim or file a formal appeal.

Key Takeaways

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CO-45 is a CO denial code — charge exceeds fee schedule.

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Always read the accompanying RARC codes for specific detail about what is missing or incorrect.

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Most denials are resolved via corrected claim submission, not formal appeal.

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Document all follow-up actions and track the claim to resolution within timely filing limits.

Denial Code Definition

CO-45 is a CARC indicating that the provider's billed charge exceeded the maximum allowable amount under the payer's fee schedule, contracted rate, or legislated fee arrangement. The payer adjusts the charge down to the contracted rate, and the difference is typically a contractual write-off — not patient responsibility.

Official Description

Charge exceeds fee schedule / maximum allowable or contracted/legislated fee arrangement. (Use code 45 to show the dollar amount.)

Why This Denial Occurs

This is a standard contractual adjustment, not a true denial. It occurs when a provider's billed charges are higher than the contracted or fee schedule rate. Every claim where billed charges exceed the contracted rate will show a CO-45 adjustment. It only becomes a problem if the adjustment is incorrect or if the provider is out-of-network.

Medicare-Specific Causes

Medicare uses the MPFS, which updates annually. Medicare applies MPPR for therapy services (50% reduction for second and subsequent procedures) and for surgical procedures. Bilateral procedures are paid at 150% of the fee schedule amount.

1Billed charges exceed the Medicare Physician Fee Schedule (MPFS)
2Multiple procedure payment reduction (MPPR) for therapy or surgical procedures
3Bilateral procedure adjustment (150% rule)
4Outdated or incorrect fee schedule year applied

Required Documentation

Provider contract or fee schedule showing the agreed-upon rates
ERA/EOB showing the contracted rate and adjustment amount
Patient assignment of benefits (if applicable)
Itemized billed charges for verification

Investigation Workflow

1Review the ERA/EOB to confirm the CO-45 adjustment amount.
2Compare the allowed amount to your contracted fee schedule for that CPT code.
3Verify the provider was in-network at the time of service.
4Check if multiple procedure reductions or bilateral adjustments were applied correctly.
5Confirm the patient is not being billed for the contractual write-off.
6If the allowed amount appears incorrect, verify the CPT code and fee schedule year.

Resolution Steps

1If the adjustment is correct: write off the contractual adjustment and bill the patient only for copay/coinsurance/deductible.
2If the allowed amount is lower than your contracted rate: file an appeal with your contract and fee schedule as documentation.
3If the provider was incorrectly processed as out-of-network: submit a corrected claim with proof of credentialing and network status.
4If multiple procedure reductions were incorrectly applied: appeal with documentation showing correct coding and bundling rules.

Appeal Guidance

CO-45 is not typically appealable — it reflects a contractual rate. However, appeal if: (1) the allowed amount is below your contracted rate, (2) the provider was incorrectly processed as out-of-network, (3) fee schedule reductions were incorrectly applied, or (4) the wrong fee schedule year was used. Provide your contract and fee schedule as evidence.

Medicare Appeal Tip

For Medicare CO-45 disputes, verify the MPFS rate on the CMS website for the specific CPT code and locality. If Medicare applied the wrong fee schedule year or locality, file a reopening (not a full appeal) with the MAC.

Prevention Strategies

Ensure your billing system is loaded with current contracted rates for each payer.
Regularly audit ERA postings to confirm CO-45 adjustments match your contract.
Verify patient eligibility and network status before the visit.
Train staff to distinguish contractual write-offs (CO-45) from patient responsibility (PR) adjustments.
Conduct annual contract rate reviews and negotiate underpayments.
Flag and investigate any CO-45 adjustment that exceeds expected percentages.

Real-World Scenario: Medicare

Situation

A therapy practice billed CPT 97110 and 97112 for the same session. Medicare paid the first code at 100% and the second at 50% per MPPR rules, resulting in a CO-45 adjustment.

Resolution

The biller confirmed the MPPR was applied correctly per Medicare rules. The contractual write-off was posted, and the patient was billed only for coinsurance. No appeal was necessary — the adjustment was accurate.