Claim adjustment reason code · X12

CO-22: may be covered by another payer.

CARC 22 says the payer believes another payer may be responsible under coordination of benefits. Confirm which plan is primary, bill that plan first, and send this payer the other plan's payment details.

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

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What X12 says CARC 22 means

This care may be covered by another payer per coordination of benefits.

CARC 22 · Start 01/01/1995, last modified 09/30/2007.

In plain terms: The payer thinks another plan should pay first or pay as well. Check coordination of benefits.

What it means on a remittance

Coordination of benefits (COB) decides the order in which plans pay when a patient has more than one. When this payer's file shows other coverage that comes first, it holds the claim back and reports CARC 22. The code does not say the service is non-covered; it says the order may be wrong or the other payer's result is missing.

Typical causes

The patient has a second plan (employer plan, spouse's plan, Medicare, Medicaid) that the claim does not show.
The claim lists this payer as primary but this payer's records show it as secondary.
The patient's COB questionnaire on file with the payer is out of date.
An accident or work-related injury where another carrier may owe first.

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

What to check

Ask the patient for all current cards and verify eligibility with each payer for the date of service.
Ask this payer who it has on file as primary, and the date it recorded that.
Check whether the claim has the other payer's name, ID and payment details in the right fields.
Check the filing clock for each payer you now have to bill.

Correct, resubmit or appeal

Bill the primary payer first. When it responds, send this payer the claim with the primary's payment and adjustment details (or its explanation of benefits when the payer asks for paper). If the payer's COB record is wrong, the patient usually has to update it with the payer, which then reprocesses. Medicare's one-calendar-year filing rule (42 CFR 424.44) keeps running during COB, so use the calculator for the deadline. Redetermination of a Medicare denial is 120 days from receipt of the notice.

Medicare dates that apply

Medicare claims must be filed no later than the close of the period ending 1 calendar year after the date of service (42 CFR 424.44(a)(1)), with exceptions in 424.44(b). A redetermination request must be filed within 120 calendar days from the date a party receives the notice, receipt is presumed 5 days after the notice date (42 CFR 405.942(a)), and a late request can be considered for good cause (405.942(b)). Clerical errors, including inaccurate data entry, are handled by the contractor as reopenings instead of redeterminations (42 CFR 405.980(a)(3)). The tool above runs the date math.

Related codes

X12 does not publish a table that pairs each CARC with remark codes; the payer picks the remark code and prints it beside the CARC on the same remittance line. These X12 remark codes carry wording that speaks to this reason, so look for them:

N4 — Missing/Incomplete/Invalid prior Insurance Carrier(s) EOB.
N479 — Missing Explanation of Benefits (Coordination of Benefits or Medicare Secondary Payer).
N480 — Incomplete/invalid Explanation of Benefits (Coordination of Benefits or Medicare Secondary Payer).
MA64 — Our records indicate that we should be the third payer for this claim. We cannot process this claim until we have received payment information from the primary and secondary payers.

Other codes: CARC 109 (claim sent to the wrong payer), CARC 29 (filing deadline expired). The full lookup reads any code on this page.

Worked example (hypothetical)

A patient is covered by a spouse's employer plan and a plan of their own. The claim went to the patient's own plan as primary and came back CO-22. The biller confirms the spouse's plan is primary, bills it, then sends the second claim with the first plan's payment details.

Sources

X12: Claim Adjustment Reason Codes — code text, usage notes and dates (list dated 10/30/2026, retrieved 2026-11-02)
X12: Remittance Advice Remark Codes — remark code text (retrieved 2026-11-02)
42 CFR 424.44, 42 CFR 405.942 and 42 CFR 405.980 — 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. Every rule above was read from these pages on November 2, 2026. Payers revise code lists, contracts and policies, so confirm anything that affects a claim or a deadline with the payer.

Frequently asked questions

Does CO-22 mean the claim is denied for good?

No. It says another payer may be responsible. Once the right payer pays first, the claim is normally resubmitted with that payer's results.

Who decides which plan is primary?

The plans' coordination of benefits rules and, for Medicare, the Medicare Secondary Payer rules decide. Ask each payer to confirm what it has on file instead of guessing.

Does the filing deadline pause while I sort out COB?

Do not assume it does. Medicare's rule in 42 CFR 424.44 counts one calendar year from the date of service. Other payers set their own limits in their contracts.

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.