CO-45 Denial Code: Charge Exceeds Fee Schedule / Maximum Allowable
CO-45 means the charge exceeds the fee schedule, maximum allowable, or contracted/legislated fee arrangement. It is a contractual adjustment, not a true denial: if you bill $200 and the contracted rate is $120, the $80 difference posts as CO-45 and cannot be balance-billed to the patient.
- Group
- CO — Contractual Obligation
- Category
- Contractual adjustment (not a payment denial)
- Appealable?
- Rarely — only when the contracted rate was misapplied
- Typical fix
- Post as write-off; dispute only true rate errors
What does denial code CO-45 mean?
CO-45 is the payer telling you: your billed charge is higher than the fee schedule, maximum allowable, or contracted rate, and the difference is being adjusted off. The official X12 description is "Charge exceeds fee schedule/maximum allowable or contracted/legislated fee arrangement." It appears on almost every paid claim from a contracted payer, because nearly every practice bills above its contracted rates.
Full guide: CO-45 denial code — complete walkthrough covers rate verification, underpayment audits, and appeal templates in depth. This card is the quick reference.
Why does CO-45 appear?
Because your chargemaster is set above the payer's allowed amount — which is intentional and correct. Example: you bill 99214 at $210, the contracted rate is $131.50. The ERA shows $131.50 allowed, and $78.50 adjusted with CO-45. Patient cost-sharing comes out of the allowed amount, never the CO-45 portion.
The dangerous version: the payer loads the wrong rate. If your contract says $131.50 but the ERA allows $112, that extra $19.50 hides inside the same CO-45 adjustment and gets auto-posted as a write-off by most PM systems.
How do you work a CO-45?
- Confirm the allowed amount matches your loaded fee schedule for that CPT and payer.
- If it matches, post the adjustment as a contractual adjustment and move on.
- If it does not match, flag it as an underpayment — do not write it off — and dispute with your rate sheet attached.
Can you prevent or appeal CO-45?
You cannot prevent it, and for correctly priced claims there is nothing to appeal. Load every payer fee schedule into your PM system so variances surface automatically, and run unrecognized codes through the denial code lookup. When a rate is genuinely misapplied, a short payment-dispute letter with the contract excerpt usually resolves it — the appeal letter generator has an underpayment template.
Frequently asked questions
No. The CO group code means contractual obligation — the amount is the provider's write-off under the payer contract. Balance-billing a CO-45 amount to an in-network patient violates your participation agreement and, for Medicare, federal limiting-charge rules.
Not in the usual sense. The claim was paid; CO-45 just explains the gap between your billed charge and the allowed amount. It only becomes a problem when the adjustment is larger than your contract says it should be, which means the payer priced the claim at the wrong rate.
Appeal when the paid amount does not match your fee schedule: wrong contracted rate loaded, out-of-network pricing applied to an in-network provider, or a multiple-procedure reduction taken twice. Pull your contract rate sheet, calculate the expected allowable, and dispute with the math attached.
Sources & further reading
Reviewed by the ImmediCare Solutions RCM team
Certified billers and coders handling claims across 50+ specialties nationwide. This entry is reviewed against current payer policy and CMS rules. Last review: Jul 5, 2026.
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