Claim adjustment reason code · X12

CARC 45: charge exceeds fee schedule.

CARC 45 is usually not a denial. It is the gap between what you billed and what the payer allows under its fee schedule or your contract. With group code CO the gap is a write-off; with PR it is the patient's share.

Sources: X12, CMS and eCFR · retrieved November 2026Runs in your browser · nothing is sent or stored

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What X12 says CARC 45 means

Charge exceeds fee schedule/maximum allowable or contracted/legislated fee arrangement.

CARC 45 · Start 01/01/1995, last modified 07/01/2017.

X12 usage note: This adjustment amount cannot equal the total service or claim charge amount; and must not duplicate provider adjustment amounts (payments and contractual reductions) that have resulted from prior payer(s) adjudication. (Use only with Group Codes PR or CO depending upon liability)

The usage note matters in practice. The 45 amount cannot equal the whole charge, and it must not repeat reductions a prior payer already took. So a line where 45 equals the full charge is a sign the payer coded something else wrongly, not a normal fee-schedule cut.

CO-45 versus PR-45

X12 limits CARC 45 to two group codes, PR and CO, "depending upon liability". X12 names these groups Patient Responsibility and Contractual Obligation. In everyday billing, CO-45 is the contractual write-off you cannot bill to the patient, and PR-45 is an amount the patient may owe. Which one applies is set by the payer and your agreement, so read the group code before you post the adjustment. The code lookup explains all four group codes.

Worked example (hypothetical numbers)

You bill $200.00 for an office visit. The payer's allowed amount is $120.00. The remittance shows CO-45 for $80.00. The patient's coinsurance is 20 percent of the allowed amount, which is $24.00, shown as PR-2. The payer pays $120.00 minus $24.00, or $96.00. You collect $96.00 from the payer and $24.00 from the patient, and write off $80.00. Billing the patient for the $80.00 would be wrong under CO.

What to check when the amount looks wrong

Compare the allowed amount on the remittance with the rate in your contract or the published fee schedule for that code, modifier and date of service.
Check units and modifiers. A wrong modifier or unit count changes the allowed amount. See CARC 4 when the payer says the modifier does not fit the code.
Check that the contract is loaded at the right effective date in your billing system.
If the allowed amount is below contract, ask the payer for a reprocessing review and cite the contract term. Do not write off the difference until you have an answer.

What this page does not do

It does not know your contract rates or any payer's fee schedule. It explains the published code and the group code so you can read a remittance correctly.

Sources

X12: Claim Adjustment Reason Codes — code text, start and last-modified dates (list dated 10/30/2026, retrieved 2026-11-01)
X12: Claim Adjustment Group Codes — CO, OA, PI, PR names (retrieved 2026-11-01)

Every code description and rule above was retrieved from these pages on November 1, 2026. Payers revise code lists, contracts and policies, so confirm anything that affects a claim or a deadline with the payer.

Frequently asked questions

Is CARC 45 a denial?

Not usually. It records the difference between the charge and the payer's allowed amount. The claim can still be paid in full at the allowed amount.

Can I bill the patient for the CARC 45 amount?

Not under group code CO, which X12 calls Contractual Obligation. Under PR, which X12 calls Patient Responsibility, the patient may owe the amount. Confirm with the payer if the group code looks wrong.

What if CARC 45 equals the full charge?

X12 says the 45 amount cannot equal the total service or claim charge. Ask the payer why it used 45 and request the correct reason code.

Not legal, billing or medical advice

This page explains published code lists and rules and runs a lookup in your browser. It cannot see your claim, your contract or any payer's policy. Confirm with the payer or your Medicare Administrative Contractor before you resubmit, appeal or bill a patient.