What does denial code CO-27 mean?

CO-27 means the patient's coverage under this plan had already terminated before the date of service, so the payer has no obligation for the claim. Retroactive terminations are common, which is why the exact termination date matters.

Can I bill the patient after a CO-27 denial?

Only after establishing that no replacement coverage existed for the date of service. Most terminations are transitions to a new employer plan, Medicare, or a marketplace plan, and the new plan is the correct payer. Document the search before converting the balance to self-pay.

CO-27: Expenses were incurred after coverage terminated

CO-27 is a coverage-date denial and one of the few where the balance genuinely can end up with the patient - but only after the question of a replacement plan is settled. Termination rarely means the patient has no insurance; far more often they moved to a new employer's plan, aged into Medicare, or transitioned to a marketplace plan. Statementing the patient before checking is how practices bill people who were covered the entire time by someone else.

What it means: The patient's coverage under this plan had already ended on the date the service was delivered.
Who pays the balance: Contractual against this payer; the balance moves to a replacement plan or, where none exists, to the patient as self-pay.
Group code CO: Contractual Obligation - the provider absorbs the balance and cannot bill the patient

Why CO-27 happens

The patient changed jobs and the old plan terminated at the end of the prior month.
Premiums went unpaid and the plan terminated retroactively, sometimes after the claim was already submitted.
The patient aged off a parent's policy or a dependent lost eligibility.
Coverage moved to Medicare or a marketplace plan and the practice's record was never updated.
Eligibility was verified before the visit but the termination was loaded by the payer afterwards with a retroactive date.

How to fix a CO-27 denial

1
Confirm the termination date directly with the payer
Retroactive terminations are common and the date matters, because a service one day before the termination is payable and one day after is not.
2
Find the replacement coverage before anything else
Contact the patient for current insurance. Most terminations are transitions rather than losses, and the new plan is usually the correct payer for the date of service.
3
Check for retroactive reinstatement
Coverage terminated for non-payment is frequently reinstated once premiums are caught up. If it was reinstated back through the date of service, ask the payer to reprocess rather than rebilling elsewhere.
4
Convert to self-pay only when no coverage existed
Document the search for replacement coverage before moving the balance. Apply the practice's self-pay or financial assistance policy consistently rather than treating the full charge as the amount due.

Deadlines depend on the payer

Filing limits and appeal windows for CO-27 vary by payer and often by plan type within the same payer. Look up the specific payer to see its verified deadlines and the source document they came from.

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Preventing CO-27 denials

Verify eligibility for the specific date of service at every visit, not only at registration.
Re-verify before high-cost scheduled services, where a termination discovered afterwards is most expensive.
Build a workflow that asks about insurance changes at check-in rather than assuming the record is current.

CO-27 frequently asked questions

What does denial code CO-27 mean?: CO-27 means the patient's coverage under this plan had already terminated before the date of service, so the payer has no obligation for the claim. Retroactive terminations are common, which is why the exact termination date matters.
Can I bill the patient after a CO-27 denial?: Only after establishing that no replacement coverage existed for the date of service. Most terminations are transitions to a new employer plan, Medicare, or a marketplace plan, and the new plan is the correct payer. Document the search before converting the balance to self-pay.

Related denial codes

PR-26 CO-31 CO-109 CO-140 PR-200

Last reviewed August 5, 2026.

Denial code explanations are original plain-English summaries written for reference and are not the official X12 code descriptions. Payer handling of any code varies by contract - always verify against the remittance advice and your payer agreement before adjusting a claim.