CO-45: Charge exceeds fee schedule or contracted amount

What it means

CO-45 is the standard contractual adjustment. It represents the difference between what you billed and the maximum allowable amount under the fee schedule or your negotiated contract. This is normal on in-network claims and is not a denial of the service.

Mechanically the payer prices the line to the allowed amount and reports the remainder as CO-45. As a CO code this amount is written off and cannot be balance billed to the patient. It only becomes a problem when the allowed amount looks wrong versus your contracted rate.

Why it happens in behavioral health

For behavioral health this appears on essentially every in-network claim and is usually expected. The attention point is when the CO-45 write-off is larger than your contract says it should be, which signals a loaded fee schedule or a rate that was not updated after contract renegotiation.

IOP, PHP, and residential per diem and bundled rates are common places where posted allowed amounts drift from the contracted rate. Reconcile CO-45 adjustments against your loaded fee schedule so systematic underpayments on high-volume codes are caught rather than written off silently.

How to fix it

• Confirm the allowed amount matches your contracted rate for that code and place of service.
• If the allowed amount is correct, post the CO-45 as a contractual write-off and move on.
• If it is lower than your contract, gather the fee schedule and dispute the underpayment with the payer.
• Escalate repeated underpricing on the same code to your provider relations contact.

How to prevent it

• Load contracted rates into your billing system and reconcile CO-45 against them.
• Audit allowed amounts after every contract renegotiation to catch stale fee schedules.
• Monitor high-volume IOP and PHP codes for systematic underpayment patterns.

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