A CO-27 denial says the patient’s coverage ended before the date of service. The right response depends on the eligibility history, claim dates, responsible payer and any later reinstatement. Correcting the claim without resolving those questions can produce another denial or an inaccurate patient balance.
Billing teams should begin with the remittance, then verify coverage for the specific service date rather than relying on current status. The goal is to establish what coverage existed and choose the correct response: correction, submission to another payer, reprocessing or appeal.
What does the CO-27 denial code mean?
The CMS standardized Claim Adjustment Reason Code reference defines CARC 27 as “Expenses incurred after coverage terminated.” It generally appears when the payer’s system shows that the member’s policy or benefit period ended before the billed service date.
The “CO” group code identifies the adjustment as a contractual obligation in that payer’s adjudication. It does not prove that the patient can be billed. Review the entire remittance, including related codes, affected lines, policy references and instructions.
CARC 26 concerns expenses incurred before coverage began, while CARC 27 applies to expenses incurred after coverage terminated. The payer’s full message and eligibility history determine which situation applies.
Why CO-27 denials happen
Coverage ended before the date of service
The policy may have terminated after an employment change, plan-year transition, premium issue, age limit or another eligibility event. If service occurred after the confirmed termination date, the billed payer may not be responsible.
Outdated or mismatched patient information
The registration record may contain an old member ID, group number or payer name. A patient may present a previous insurance card even though a new plan became active. The claim can then reach a payer whose coverage was no longer in force.
Retroactive termination or reinstatement
Eligibility can change after the visit. A plan may retroactively terminate coverage and later reinstate it after a correction or premium resolution. A claim submitted during the transition may deny even when later eligibility supports coverage.
Coordination-of-benefits information is incomplete
The patient may have another active plan, Medicare, Medicaid or coverage through a spouse. If the wrong payer was treated as primary, the claim may need coordination-of-benefits correction and submission to the responsible payer.
The claim spans covered and uncovered dates
Institutional or recurring-service claims can cross a termination date. Some payers require eligible and ineligible periods to be separated. Review every service line and date rather than assuming the entire claim has the same eligibility status.
What to review before taking action
Start with the denial as received. Capture the payer, affected line, date of service, amount, group code, CARC, any RARC, trace number and instructions. A remark code may identify needed eligibility evidence, a member identifier issue or another plan.
Compare the remittance with the claim accepted by the payer. Confirm the patient, member and group numbers, payer ID, subscriber relationship, service dates, provider information and claim frequency. An error can make a valid member appear ineligible.
Use the payer portal or an approved eligibility transaction to verify coverage for the date of service. CMS’s Checking Medicare Eligibility guidance explains that Medicare eligibility systems provide entitlement, plan and related information that providers should review before billing. Save the dated response or reference number when it supports the claim.
Ask whether another payer was active and whether coordination-of-benefits data was current. Establish which plan was responsible on the service date and in what order.
A practical CO-27 denial resolution workflow
1. Read the complete payer message
Determine whether CO-27 applies to the whole claim or selected lines. Record related codes and instructions that may change the resolution path.
2. Verify the patient and policy details
Match the claim to the insurance card, registration record and payer file. Look for transposed digits, an old member number, an incorrect subscriber relationship or a payer ID associated with a former plan.
3. Confirm eligibility on the exact service date
Request historical, date-specific eligibility. Confirm the effective date, termination date, plan type and benefit status. A current eligibility screen is not enough when the service occurred weeks or months earlier.
4. Reconcile coverage changes and other insurance
Review employer updates, replacement-plan information, Medicare or Medicaid status and coordination-of-benefits records. Contact the payer when its data conflicts with the patient’s evidence.
5. Choose the correct claim path
If claim data was wrong, submit the payer’s required corrected claim. If another payer was responsible, bill that payer and preserve timely-filing evidence. If the payer used an incorrect termination date, request reprocessing or appeal with documentation.
6. Protect filing and appeal deadlines
Record deadlines while coverage questions are investigated. CMS’s Medicare Parts A and B appeals process illustrates the formal levels and time-sensitive nature of Medicare review. Commercial and Medicaid plans have their own rules.
7. Document the outcome
Record eligibility responses, call references, representative names, portal screenshots, submission dates and the final payer determination. Update registration and claim-scrubbing rules when the denial reveals a repeatable front-end issue.
Should a CO-27 claim be corrected, rebilled or appealed?
Correct the claim when inaccurate member, payer or date information caused the denial. Use the payer’s replacement-claim frequency and original claim reference requirements; do not submit an unchanged duplicate.
Bill the correct payer when date-specific verification shows that another plan was responsible. Include prior-payer information when coordination-of-benefits rules require it and retain proof that the first payer denied or redirected the claim.
Appeal or request reprocessing when the submitted claim was accurate but the payer used an incorrect termination date, failed to recognize reinstated coverage or overlooked valid coordination information. RCMGen’s claim-denial appeal framework explains how to organize the denial, policy basis, evidence and requested action without turning an appeal into a general complaint.
Do not automatically move the balance to the patient. First confirm the group code, contract, plan rules, required notices and applicable law. A payer’s CO adjustment may restrict patient billing even when coverage truly ended.
How billing teams can prevent repeat CO-27 denials
Verify eligibility before the visit and again close to the service date when coverage may change. RCMGen’s guide to eligibility verification in medical billing outlines the practical details that front-end teams should confirm, including member identity, effective dates, plan status and benefit information.
Build registration prompts for recent employment or plan changes, capture both sides of the current insurance card and verify subscriber relationships. Recheck eligibility for recurring services, scheduled procedures and claims that span month-end or plan-year transitions.
Track CO-27 denials by payer, location, registration team, service date and root cause. Trends can reveal stale insurance records, weak coordination-of-benefits workflows, missed historical eligibility checks or payer files that need escalation.
How RCMGen approaches CO-27 denial resolution
RCMGen treats CO-27 as a date-specific eligibility investigation rather than a routine write-off. Its denial management workflow connects the remittance, historical eligibility, registration record, coordination-of-benefits information and filing limits before the team chooses correction, rebilling or appeal.
The same findings should feed prevention. When a denial traces to outdated coverage data or a missed verification step, the useful outcome is not only resolving one claim but also correcting the upstream workflow that created it.
Frequently asked questions about the CO-27 denial code
What does CO-27 mean on a medical claim?
CARC 27 means the payer determined that the expenses were incurred after coverage terminated. The CO group code shows how the payer classified the adjustment, but the full remittance and contract must be reviewed before deciding liability.
Is the patient automatically responsible for a CO-27 denial?
No. Verify the group code, eligibility history, provider contract, notices and payer rules first. The denial may result from incorrect payer data, retroactive coverage changes or a coordination-of-benefits issue.
What is the difference between CARC 26 and CARC 27?
CARC 26 applies when expenses were incurred before coverage began. CARC 27 applies when expenses were incurred after coverage terminated. Verify the effective and termination dates for the exact date of service.
Can retroactive reinstatement resolve CO-27?
Yes, when the plan later confirms coverage for the service date. Obtain a dated eligibility response or written confirmation and follow the payer’s reprocessing, corrected-claim or appeal instructions.
What evidence supports a CO-27 appeal?
Useful evidence may include historical eligibility results, insurance cards, employer or plan letters, premium or reinstatement records, coordination-of-benefits confirmation, the original accepted claim and documented payer call references.
Should billing teams correct the claim or appeal it?
Correct the claim when submitted data was wrong. Appeal or request reprocessing when the claim was accurate and the payer’s termination or eligibility record was incorrect. Bill another payer when verified coverage shows that it was responsible.
Resolve CO-27 denials with date-specific coverage evidence
CO-27 resolution begins with one question: what coverage was active on the exact date of service? Once billing teams reconcile the remittance, historical eligibility, claim data and payer order, they can choose the right action without creating duplicates or inappropriate patient balances. Documenting the result also turns each denial into a practical improvement for registration, eligibility verification and claim follow-up.