CO-45: Charge exceeds fee schedule or maximum allowable amount

CO-45 looks scary on an EOB because it can show a large dollar amount adjusted. In most cases, it is a contract adjustment between the plan and the provider, not a balance you owe. Here is how to read it.

Read the EOB carefully

CO-45 usually appears in the "Adjustments" column of your EOB. The columns tell the story:

• Billed: the provider's list price
• Allowed: what the plan and the provider agreed on
• Adjustment (CO-45): the difference the provider writes off under the network contract
• Plan Paid: what the plan actually paid
• Member Responsibility: what you owe

If CO-45 is a contract adjustment and your Member Responsibility line is $0 or a small copay, this is not a denial. You do not need to appeal.

When CO-45 is actually your problem

CO-45 becomes something to push back on when:

• The provider is billing you for the CO-45 amount (potential "balance billing," which is illegal in many states and under the No Surprises Act for many emergency and out-of-network scenarios)
• The provider is out of network and the CO-45 leaves you with a large "Member Responsibility"
• The plan calculated the allowed amount using an unreasonably low fee schedule for the region

What your letter emphasized

• Whether the provider is in-network (in which case, the write-off is contractual and no appeal is needed)
• If out-of-network: your plan's out-of-network benefit structure, plus No Surprises Act protection if applicable
• The specific fee schedule the plan used, and whether it appears reasonable compared to regional benchmarks
• Any billing error that resulted in the wrong CPT code being used

What the insurer's likely response is

No action needed. For an in-network provider, the plan often responds that CO-45 is a normal write-off and you owe nothing.

Reprocessed at higher allowed amount. Sometimes the plan agrees the fee schedule was too low or the wrong code was applied and reprocesses.

Upheld with an explanation. The plan sends a longer explanation of the fee schedule methodology. This is worth reading; it can inform a state DOI complaint about network adequacy.

How to handle each outcome

In-network, no member balance: you are done.

Reprocessed: confirm on the new EOB and, if needed, ask the provider to update the balance they show you owe.

Upheld, out-of-network, No Surprises Act eligible: file a No Surprises Act complaint at cms.gov/nosurprises. This applies to most emergency services and some non-emergency services at in-network facilities.

Upheld, provider balance-billing you: file a state DOI complaint. Many states prohibit balance billing.

No Surprises Act quick reference

Since 2022, the No Surprises Act protects patients from surprise out-of-network bills in specific situations:

• Emergency services at any hospital, in-network or out
• Non-emergency services at an in-network facility from an out-of-network provider (unless you gave written consent)
• Air ambulance services

If your CO-45 stems from any of those, you may not owe the balance. Contest the bill with the provider and, if needed, escalate.

What to gather

• The full EOB showing all columns
• The provider's bill (to see if they are billing you for the CO-45 amount)
• Your insurance card (to confirm the plan)
• The provider's network status (call the plan or check the online directory as of the date of service)

When to skip an appeal

If your Member Responsibility line is small or zero, do not appeal. The CO-45 is administrative. Appeals expend energy that is better saved for real denials.