Glossary · Denial and adjustment codes
What is denial code CO-27?
CO-27 means the service happened after the patient's coverage ended. The fix is finding the coverage that was active on the date of service.
Example · fictional data
A claim denied because the employer plan ended at the end of the month.
Remittance advice, claim line
- Coverage
- Employer PPO, ended 01/31/2026
- Date of service
- 02/06/2026
| Service | Billed | Paid | Adjustment |
|---|---|---|---|
| 99214 Office visit | $210.00 | $0.00 | CO-27 $210.00 |
- Insurance discovery found a marketplace plan active from February 1. Bill it now, before its filing limit.
Reason code 27 reads: Expenses incurred after coverage terminated.
Why it happens
Patients change jobs, lose Medicaid eligibility, age into Medicare or switch plans at the start of the year, and nobody tells the front desk. The claim goes to the plan on file, which no longer covers them.
How to resolve it
- Check eligibility for the date of service, not today.
- Search for the new coverage with insurance discovery or by asking the patient.
- Bill the right payer quickly; the new payer’s filing limit has been running since the service.
- If no coverage existed, the balance belongs to the patient.
How to prevent it
Verify coverage before every service, not just the first, and recheck patients whose coverage is likely to change, such as at the start of a year.
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