CO-45 Denial Code: Charge Exceeds the Fee Schedule or Contracted Rate
The CO-45 adjustment code means the billed charge exceeded the payer's fee schedule, maximum allowable, or contracted rate - the payer paid its allowed amount and CO-45 accounts for the difference. Strictly speaking it is a contractual adjustment, not a denial: seeing CO-45 on a paid line is completely normal. It only needs investigation when the allowed amount looks wrong for your contract.
Common Causes
- Routine contractual difference between the practice's charge master and the payer's allowed amount (normal, expected)
- The claim priced against the wrong fee schedule - out-of-network rates, an outdated contract, or the wrong provider tier
- Multiple-procedure payment reductions applied to second and subsequent procedures
- The payer's allowed amount changed after a contract update your billing system has not loaded
- Charge-entry errors, such as billing an amount below the contracted rate (you are paid the lesser of billed vs allowed)
How to Fix CO-45
- First decide if action is needed at all: compare the allowed amount on the remit against your contracted rate for that code
- If the allowed amount matches the contract, post the CO-45 amount as a contractual write-off - do not bill the patient for it
- If the allowed amount is lower than your contracted rate, appeal or request a reprocessing with the contract language and rate exhibit
- Verify the claim priced in-network - a network or credentialing glitch that prices you out-of-network shows up as an oversized CO-45
- Keep contracted fee schedules loaded in the billing system so underpayments are flagged automatically at posting
Frequently Asked Questions
CO-45 means the charge exceeds the fee schedule or contracted maximum. It is the standard contractual adjustment showing the gap between what you billed and what the payer allows - on most remits it appears on paid claims and requires no action.
Usually no. It is a contractual adjustment that appears alongside a payment. It becomes a problem only when the allowed amount is below your contracted rate - then you appeal the pricing, not the adjustment code itself.
No. The CO group code marks it a contractual obligation - balance billing the difference violates in-network contracts. The patient owes only their cost-share amounts, which appear under PR codes (deductible PR-1, coinsurance PR-2, copay PR-3).
Related Denial Codes
Related Resources
Claim adjustment reason codes and remittance advice remark codes are standardized code sets maintained by X12. The explanations on this page are written in our own words for educational purposes, based on public CMS and Medicare contractor documentation. Payer policies vary - always confirm handling with the specific payer's guidance and your contracts.