CO-27 denial: coverage terminated before the service
The payer says the patient's coverage had already ended on the date of service.
Expenses incurred after coverage terminated.
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?
Winnable when coverage was actually active and the payer's file is wrong — which happens more than people expect, particularly around plan changes and retroactive reinstatements. When coverage genuinely had ended, the amount usually becomes the patient's responsibility rather than an appeal.
Why payers issue CO-27
- 01Coverage genuinely ended before the date of service.
- 02The payer's eligibility file had not yet processed a reinstatement or renewal.
- 03The patient changed plans within the same payer and the claim went to the terminated plan.
- 04Retroactive termination was applied after the service was already provided.
What to gather before you appeal
- The eligibility verification captured at the time of service, with the date it was run.
- The patient's insurance card and any updated coverage information.
- Written confirmation of reinstatement, where applicable.
- The payer's stated termination date, to compare against the date of service.
Arguments that work
- Coverage was verified active on the date of service — here is the verification record.
- Coverage was reinstated retroactively and now covers the date of service.
- The claim was routed to the wrong plan within the same payer.
The deadline
Move fast on these for a second reason: if coverage really had ended, the sooner you know, the more time you have to bill the correct payer inside its timely filing window.
Common questions about CO-27
- Can I bill the patient if their coverage had ended?
- Often yes, but not automatically — it depends on the payer contract and what the patient was told at check-in. This is one of the few denials where the money is genuinely recoverable from a source other than the payer.
- How do I stop CO-27 from recurring?
- Verify eligibility on the date of service and keep the verification record. That record is the entire appeal when a payer's file later disagrees.
Draft the CO-27 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.
Other denial codes
- CO-197CO-197 denial: prior authorization absent
- CO-16CO-16 denial: claim lacks information
- CO-29CO-29 denial: timely filing limit expired
- CO-45CO-45: charge exceeds fee schedule
- CO-50CO-50 denial: not deemed medically necessary
- CO-97CO-97 denial: service already included in another payment
- CO-18CO-18 denial: exact duplicate claim
- CO-22CO-22 denial: another payer is primary
- CO-96CO-96 denial: non-covered charges
- CO-109CO-109 denial: claim sent to the wrong payer
- CO-151CO-151 denial: too many services billed
- CO-B7CO-B7 denial: provider not eligible on the date of service
- CO-4CO-4 denial: modifier inconsistent or missing
- CO-11CO-11 denial: diagnosis inconsistent with the procedure
- PR-1PR-1: deductible amount — and why it is not a denial
- PR-204PR-204: not covered under the patient's benefit plan