Official CARC description: “Charge exceeds fee schedule/maximum allowable or contracted/legislated fee arrangement.” Here’s what it actually means, why it fires, and how to get the claim paid.
CO 45 is usually not a denial at all — it's the contractual write-off between your charge and the allowed amount. It becomes a problem when the payer applies the wrong fee schedule, prices you as out-of-network, or the “write-off” quietly swallows money your contract owes you.
Liability group: CO = Contractual Obligation — the provider absorbs it — the amount cannot be billed to the patient. If the denial is wrong, the money is recovered by correcting or appealing the claim, not by balance-billing.
Also written: CO-45, CO45, “denial code 45”, “45 denial code” or “reason code 45” — same CARC, different ERA formatting.
Compare the allowed amount to YOUR contracted rate for that CPT — not just the EOB math
If the rate is wrong: request reprocessing with the contract section attached
If processed OON incorrectly: fix the roster/enrollment and reprocess
Track CO 45 write-off percentages by payer monthly — drifts reveal repricing errors
Appeal only when the pricing is provably wrong: attach the fee schedule page or contract rate exhibit and demand reprocessing at the contracted rate. Routine CO 45 on correctly priced claims is a write-off, not an appeal.
Fill in the denial facts — use placeholders, never real patient data (the letter keeps [PATIENT NAME]-style fields so you can merge real details privately). A payer-ready draft with an enclosure checklist comes back in ~20 seconds.
Your appeal letter draft will appear here.
The official CARC description for CO 45 is: “Charge exceeds fee schedule/maximum allowable or contracted/legislated fee arrangement.” In practice: CO 45 is usually not a denial at all — it's the contractual write-off between your charge and the allowed amount. It becomes a problem when the payer applies the wrong fee schedule, prices you as out-of-network, or the “write-off” quietly swallows money your contract owes you.
Denial code 45 under the CO group (Contractual Obligation) means: Charge exceeds fee schedule/maximum allowable or contracted/legislated fee arrangement. The number is the reason; the CO prefix decides who is liable — the provider absorbs it — the amount cannot be billed to the patient. If the denial is wrong, the money is recovered by correcting or appealing the claim, not by balance-billing.
Yes. CO 45, CO-45, CO45 and “denial code 45” are the same CARC — clearinghouses, payer portals and PM systems just print it differently. Only the group prefix (CO, PR, OA or PI) changes the meaning, because it changes who has to absorb the amount.
CO stands for Contractual Obligation — the provider absorbs it — the amount cannot be billed to the patient. If the denial is wrong, the money is recovered by correcting or appealing the claim, not by balance-billing.
Appeal only when the pricing is provably wrong: attach the fee schedule page or contract rate exhibit and demand reprocessing at the contracted rate. Routine CO 45 on correctly priced claims is a write-off, not an appeal.