What is the fastest way to clear a CO-22?

Usually the patient, not the practice. These denials often persist because the patient has not answered the payer's coordination-of-benefits questionnaire, and no amount of documentation from the practice will resolve it until they do.

Can I bill the patient for a CO-22?

No. It is a contractual adjustment, and the amount is not the patient's responsibility simply because coverage order is unclear.

CO-22Sometimes worth appealing

CO-22 denial: another payer is primary

The payer thinks someone else is primary and wants that payer to process the claim first.

Official X12 description

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

What the CO group code means

CO — Contractual Obligation

The amount is written off under your contract with the payer. You cannot bill the patient for it.

Is it worth appealing?

Usually resolved rather than appealed. If the payer's coordination-of-benefits record is wrong or stale, correcting it is faster than a formal appeal — but when the payer insists incorrectly, the appeal is straightforward and evidence-based.

Why payers issue CO-22

01The patient has, or recently had, secondary coverage the payer believes is primary.
02The payer's coordination-of-benefits file is out of date and still lists terminated coverage.
03The patient never responded to the payer's coordination-of-benefits questionnaire.
04A workers' compensation, auto, or liability claim is suspected for the same episode.

What to gather before you appeal

Current eligibility verification for the date of service.
The primary payer's remittance advice, if one exists.
Written confirmation of which coverage is primary, where the patient can supply it.
Documentation that the other coverage was terminated before the date of service.

Arguments that work

There is no other coverage — this payer is primary and its file is out of date.
The other coverage terminated before the date of service.
The primary payer has already adjudicated; here is its remittance, so process as secondary.

The deadline

Coordination-of-benefits delays are also the strongest defense against a later timely filing denial — keep the primary payer's remittance date, because most payers run the secondary filing clock from it.

Common questions about CO-22

What is the fastest way to clear a CO-22?: Usually the patient, not the practice. These denials often persist because the patient has not answered the payer's coordination-of-benefits questionnaire, and no amount of documentation from the practice will resolve it until they do.
Can I bill the patient for a CO-22?: No. It is a contractual adjustment, and the amount is not the patient's responsibility simply because coverage order is unclear.

Draft the CO-22 appeal in about three minutes

Upload the denial. Undeny reads it, drafts a payer-specific appeal letter citing this code and the record, and tracks the deadline until the money comes back.

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