What does CO-45 mean on an EOB?

CO-45 is Claim Adjustment Reason Code 45 for charge exceeds fee schedule or maximum allowable. The payer paid up to the contracted rate and reduced the excess charge.

Do I owe the difference between billed and allowed amount?

For in-network providers, you usually owe only cost sharing on the allowed amount unless plan language says otherwise. Out-of-network balance billing depends on network status, state law, and No Surprises Act rules.

Is CO-45 a medical necessity denial?

Usually not. CO-45 is a contractual rate adjustment. Medical necessity denials more often appear as CO-50 or similar non coverage codes with different appeal evidence.

Can my provider rebill CO-45?

Providers may submit a corrected claim if the wrong fee schedule, units, or modifiers were used. They cannot typically rebill simply because they charged above contract.

How do I get the fee schedule?

Ask the insurer for the allowed amount calculation and the provider for the contract rate. Some states require payers to disclose allowed amounts on request.

Does Medicare use CO-45?

Medicare remittance advice uses CARC codes including contractual adjustments. Medicare allowable amounts come from the physician fee schedule or OPPS, not commercial contract rates.

When should I appeal CO-45?

Appeal when the allowed amount is miscalculated, network status is wrong, or you were balance billed contrary to plan or state law. Attach remittance advice and itemized bills.

Can AppealFlow help with a CO-45 dispute?

Yes. Use /generate to draft a billing dispute or appeal letter citing allowed amount errors. Attach fee schedule proof and network documentation before submitting.

Denial Code Guide

CO-45 Denial: Charge Exceeds Fee Schedule

By AppealFlow editorial•Published September 2026

CO-45 charge exceeds fee schedule denial guide showing allowed amount calculation and balance billing review steps

CARC CO-45 means the payer reduced payment because the billed charge exceeds the contracted or fee schedule amount. This is usually a contractual adjustment, not a denial that the service was uncovered. Compare the allowed amount on your Explanation of Benefits to your provider contract or in-network rate. Dispute patient balance billing when state law or your plan prohibits balance billing for in-network care.

What Does CO-45 Mean on Your EOB?

Key Takeaway: CO-45 is a payment reduction to the plan allowed amount. The insurer paid up to the contracted rate and shifted any excess charge to provider write-off or patient responsibility depending on network status.

Claim Adjustment Reason Code 45 states charge exceeds fee schedule or maximum allowable. You will see it on in-network claims where the provider billed above the rate in the payer contract.

The allowed amount column on your Explanation of Benefits is the key number. Patient coinsurance and deductible usually apply to that allowed amount, not the higher charge on the provider statement.

Out-of-network bills may still show CO-45 when a payer applies a usual and customary rate before patient cost sharing. Network status and state balance billing laws determine what you may owe beyond the allowed amount.

Is CO-45 the Same as a Claim Denial?

Key Takeaway: Often the claim is paid at the contracted rate. CO-45 explains why payment is less than the billed charge, not necessarily that the service was rejected.

Many CO-45 lines show a positive plan payment with a contractual adjustment. That differs from CO-50 medical necessity denials where plan payment may be zero.

If you owe a large balance after insurance, ask whether the provider is in network, whether surprise billing protections apply, and whether the bill matches allowed amounts on the remittance advice.

When Should You Appeal CO-45?

Key Takeaway: Appeal when the allowed amount calculation is wrong, the provider was out of network without valid notice, or you were balance billed for in-network services.

Request the fee schedule excerpt, contract rate, and itemized calculation from the insurer and billing office. Compare CPT code, place of service, and modifier to the rate sheet.

File an internal appeal if the payer applied the wrong contract year, wrong network tier, or omitted units. Attach the remittance advice, provider itemized bill, and any authorization showing in-network status.

State surprise billing laws and the No Surprises Act may limit what out-of-network providers can collect in qualifying emergency and facility-based situations for most private plans.

What Documents Support a CO-45 Dispute?

Key Takeaway: Allowed amount disputes need rate proof, not clinical records unless medical necessity is also at issue.

Gather the Explanation of Benefits, provider itemized statement, payer contract summary if available, and portal screenshots showing network status at date of service.

If the provider balance bills you above the allowed amount for in-network care, cite plan language and state law in your appeal or billing dispute letter.

Documents to Gather

Key Takeaway: Attach copies of every item on this list to your appeal or give them to your provider's billing office for a corrected claim.

EOB showing CO-45 and allowed amount
Provider itemized bill with CPT codes
Network directory screenshot for date of service
Prior authorization or referral if applicable
Payer fee schedule or rate request response
Internal appeal form and mailing proof

Corrected Claim or Appeal?

Key Takeaway: Corrected claim when wrong units, modifiers, or place of service drove the wrong fee schedule. Internal appeal or billing dispute when the allowed amount math or balance billing violates contract or law.

Weak vs Strong Wording

Key Takeaway: Reviewers respond to claim numbers, dates of service, and attached records, not general complaints about fairness.

Weak	Stronger
Insurance should pay the full bill because my doctor charged more.	CO-45 reduced DOS 3/4/2026 CPT 99214 to allowed amount $142 per attached in-network contract summary. Provider billed $310. Request confirmation that patient cost sharing applies only to $142 and that in-network balance billing is prohibited under plan section 8.2.
The allowed amount seems too low.	Enclosed remittance shows CO-45 with allowed $890 for CPT 73721 while payer fee schedule for facility outpatient MRI lists $1,240 for same code and place of service. Request recalculation and reprocessing with corrected allowed amount.

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Authoritative Sources

Frequently Asked Questions

Common questions about CO-45 — Charge Exceeds Fee Schedule denials and appeals.

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Educational information only, not medical or legal advice. Denial code meanings come from standard claim adjustment reason code lists; your plan's notice and contract control appeal rights and deadlines. Full disclaimer