CO-6: procedure code inconsistent with patient age.

What X12 says CARC 6 means

The procedure/revenue code is inconsistent with the patient's age.

CARC 6 · Start 01/01/1995, last modified 07/01/2017.

X12 usage note: Refer to the 835 Healthcare Policy Identification Segment (loop 2110 Service Payment Information REF), if present.

In plain terms: The procedure or revenue code does not fit the patient's age.

What it means on a remittance

The payer compared the billed procedure or revenue code with the patient’s age, calculated from the date of birth on file, and found a mismatch. The sibling code CARC 7 covers gender; CARC 9 covers a diagnosis that does not fit the age. The X12 usage note points to the 835 Healthcare Policy Identification Segment, which can carry the payer’s policy reference for the edit.

Typical causes

• The date of birth was keyed wrongly on the claim or in registration.
• The patient is billed under the wrong person’s record, such as a parent or sibling.
• The code is meant for a defined age group, such as a pediatric or adult service, and a different code fits this patient.
• The payer’s file holds a different date of birth than your record.

These are common billing patterns, not a diagnosis of your claim. The remittance and the payer's policy decide.

What to check

1. Compare the date of birth on the claim with the patient’s record and insurance card.
2. Read the code descriptor and any age range in the code set or payer policy.
3. Look in the REF segment of the 835, if present, for the policy the payer applied.
4. Check that the claim names the patient, not the subscriber.

Correct, resubmit or appeal

If the date of birth was wrong, correct it and resubmit. If the code was wrong for the patient’s age, bill the code that matches the service. If both are right, send the payer the record that supports the service and ask for a review under its appeal process.

Medicare dates that apply

A Medicare redetermination request must be filed within 120 calendar days from the date a party receives the notice of the initial determination; receipt is presumed 5 calendar days after the notice date unless there is evidence to the contrary (42 CFR 405.942(a)), and a late request can be considered for good cause (405.942(b)). Other payers set their own appeal windows in the contract or plan documents, so read the notice for the date. The tool above runs the date math.

Related codes

X12 does not publish a table that pairs each code with remark codes; the payer picks the remark code and prints it beside the CARC on the same remittance line.

Other codes: CARC 8 (procedure vs. provider type), CARC 16 (missing or wrong claim data) and the full lookup.

Worked example (hypothetical)

A well-child visit denies with CO-6. The biller sees the date of birth was keyed with the month and day swapped, which made the patient an adult. She corrects it and resubmits.

Sources

• X12: Claim Adjustment Reason Codes — code text, usage notes and dates (list dated 10/30/2026, retrieved 2026-11-02)
• 42 CFR 405.942 — eCFR, current through 2026-10-29 (retrieved 2026-11-02)

Code descriptions are X12 copyrighted material, quoted here only for the codes on this page and linked to the owner. For the full lists, use X12. The X12 text and the Medicare rule above were read from these pages on November 2, 2026. Causes, checks and examples are general billing practice written for this page, not X12 content. Payers revise code lists, contracts and policies, so confirm anything that affects a claim or a deadline with the payer.