CO 45 denial code

Claim adjustment reason code 45. Often reported as CO 45 or PR 45.

Charge exceeds the allowed amount

Unofficial reference. This is our own plain-English explanation, not the official code text. Payer rules differ. Verify with the payer and the official X12 code list. AlphaPrefix is not affiliated with X12, CMS or any payer. Data last updated Nov 11, 2026.

What 45 means

The billed charge is higher than the payer's fee schedule or contracted rate, so the difference was adjusted off.

This is the most common adjustment on a remittance. The payer priced the service at its fee schedule or contracted amount, which is lower than what you billed, and reported the difference with this code.

It is only used with group codes CO or PR. With CO the difference is a contractual adjustment that an in-network provider normally writes off. With PR the payer is saying the patient owes the difference, which is unusual and worth checking against the contract.

Group codes seen with 45

On a remittance, 45 comes after a group code. These are the ones it is most often reported with:

• CO 45 (Contractual Obligation): The provider's side of the ledger. The reduction comes from the payer contract or a rule the provider has to follow, and the patient normally cannot be billed for it.
• PR 45 (Patient Responsibility): The amount is assigned to the patient. Deductibles, coinsurance and copays are the everyday examples. Whether you can collect it still depends on your contract and the patient's plan.

The payer chooses the group code for each adjustment, so the same reason code can appear with another group code on your remittance. Read the two together. More about group codes.

Common causes

• Your standard charge is above the payer's fee schedule for the service, which is normal for contracted providers.
• The payer priced the claim under a different fee schedule or network than you expected.
• A multiple procedure, bilateral or assistant reduction lowered the allowed amount.

What to do next

1. Compare the allowed amount on the remittance with your contracted rate for that code and date of service.
2. If the allowed amount matches the contract, post the adjustment as a contractual write-off.
3. If the payer underpaid against the contract, send a reconsideration or appeal with the fee schedule page as support.
4. Check which group code came with it before moving any balance to the patient.

Related codes

• 59 (reason code) Multiple or concurrent procedure rules
• 97 (reason code) Service included in another payment
• 23 (reason code) Prior payer payment affected this claim
• 2 (reason code) Patient's coinsurance share