CO-45
Denial Code CO-45: Charge Exceeds the Fee Schedule
Charge above the contracted allowed amount
What CO-45 officially means
Charge exceeds fee schedule/maximum allowable or contracted/legislated fee arrangement.
Source: X12 Claim Adjustment Reason Codes
What actually causes it
Your billed charge is higher than the contracted rate
This is the normal case and nothing is wrong. Practices bill a standard fee schedule and each payer allows its own contracted amount, with the difference written off.
The payer applied the wrong fee schedule
A rate loaded incorrectly, an expired contract, or a claim processed under the out-of-network schedule when you are in network. This is an underpayment wearing the same code as a routine adjustment.
The claim was processed under the wrong contract or location
Groups with multiple tax IDs, locations or specialties can have several contracts with one payer, and the claim is processed under whichever the payer matched.
How to fix it
The first thing to understand about CO-45 is that it usually means nothing is wrong. You billed 300 dollars, your contract allows 180, and 120 is written off. That is the arrangement working exactly as signed.
The reason it deserves attention anyway is that a genuine underpayment carries the same code. Nothing in the remittance distinguishes a correct contractual adjustment from a payer applying the wrong rate, and because the claim paid, no work queue flags it.
Compare the allowed amount against the contract
This is the only way to tell the two apart, and it is why the check has to be systematic rather than occasional. Take the allowed amount from the remittance and compare it against your contracted rate for that code, that payer, that location and that date of service.
Most billing systems can load contracted rates and flag variances automatically. If yours can, configure it. If it cannot, sample: pull your twenty highest volume codes per payer each quarter and check them by hand. Twenty codes per payer will find a misloaded fee schedule, and a misloaded fee schedule left running for a year is a large number.
Underpayments are worked as a project, not as claims
When you find one, do not appeal a single claim. Establish the scope first: which codes, which date range, how many claims. Then approach the payer's provider relations with the contract, the rate, and the list.
Payers correct these when they are shown clearly. What they do not do is notice them on your behalf.
Check the contract itself while you are there
Sometimes the rate is being applied correctly and the rate is simply poor. That is a contracting conversation rather than a billing one, and it needs your own data behind it: your volume with that payer, your case mix, and what comparable payers allow for the same work.
Radiology and anesthesia practices should look at this particularly closely, because both are paid through formulas rather than flat fees. Anesthesia payment turns on a conversion factor that is negotiated and locality specific, and a practice that has never verified its conversion factors against the contract is verifying nothing at all.
Do not bill the patient
The write-off portion is contractual. Billing it to the patient is balance billing, it breaches the agreement, and depending on the state and the plan it may be prohibited outright. Patient responsibility appears under its own codes, not this one.
Our accounting service reconciles payments against remittance advice specifically to surface this class of problem, because a contractual underpayment produces no denial, no alert and no complaint. It just looks like a slightly smaller deposit, every month.
Is CO-45 worth appealing?
No, correct and resubmit instead
Not appealable as a denial, because it is not one. It is the contractual difference between the billed charge and the allowed amount, and it cannot be billed to the patient. What is actionable is verifying the allowed amount against your contract: when the payer has applied the wrong rate, that is an underpayment worked through provider relations as a project across all affected claims, not as an appeal on one.
Common questions
Can we bill the patient for the CO-45 amount?
No. It is a contractual write-off, and billing it to the patient is balance billing in breach of your payer agreement. Patient responsibility comes through separate codes.
How do we know whether an allowed amount is correct?
Compare it against your contracted rate for that code, payer, location and date of service. Load your rates into your billing system if it supports variance flagging. Otherwise sample your top twenty codes per payer each quarter.
What do we do when we find a systematic underpayment?
Establish the full scope first, then approach provider relations with the contract, the correct rate and the list of affected claims. Appealing them one at a time takes far longer and gets a worse result.
See what your claims are leaving behind
Send us a month of remittance data and we will tell you what it says: which codes are being denied, how much of it is recoverable, and how long your money is sitting in A/R. It takes about a week and there is nothing to sign.