Claim adjustment reason code · X12
CARC 4: procedure code inconsistent with the modifier.
CARC 4 says the modifier on the line does not belong with that procedure code. Correct the modifier, or remove it, and send a corrected claim. Do not add modifiers only to change the outcome.
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What X12 says CARC 4 means
The procedure code is inconsistent with the modifier used.
CARC 4 · Start 01/01/1995, last modified 03/01/2020.
X12 usage note: Refer to the 835 Healthcare Policy Identification Segment (loop 2110 Service Payment Information REF), if present.
Common causes
The causes below are typical patterns, not an official list. The payer's remark code and policy are the authority.
- A modifier that is not valid for the code, for example one meant for a different type of service.
- A required modifier left off, so the code is read as inconsistent with the way it was billed.
- A typo or a stale value carried over from a charge template.
- Modifiers in the wrong order or position; some payers read the first modifier as the pricing one.
When 25 or 59 is the question
Two modifiers draw most of the denials. Modifier 25 belongs on an evaluation and management code when the visit was significant and separately identifiable from a procedure on the same day. Modifier 59 belongs on a non-E/M procedure that was distinct from another. CMS says 59 should not be appended to an E/M service and that 25 is the one for that case.
How to fix it
- Read the line the payer flagged: code, modifier, date, units.
- Check the modifier against the code in a current HCPCS or CPT reference and the payer's policy.
- Check the chart supports the modifier you bill.
- Submit a corrected claim with the right modifier. Watch the filing limit; see CARC 29.
Sources
- X12: Claim Adjustment Reason Codes — code text, start and last-modified dates (list dated 10/30/2026, retrieved 2026-11-01)
- CMS: Medicare NCCI Policy Manual, Chapter 1 (rev. 1/1/2026) — modifier 25 and 59 definitions and use (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 4 a coverage denial?
No. It is a coding inconsistency. The service may be payable once the modifier is correct.
Should I just remove the modifier?
Only if the record shows the modifier was not needed. Removing a modifier that the service requires can cause another denial or a lower payment.
Does CARC 4 apply to place of service too?
No. A mismatch between the procedure and the place of service uses a different CARC. See the place of service lookup for the code set.
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.