CO-109 denial code
Claim is not covered by this payer or contractor
How to fix it
Identify the correct payer and payer ID, then submit there. Watch the filing deadline, which runs from date of service.
How to prevent it
Verify the actual administering payer at eligibility check, including any carve-out arrangements.
In practice
A claim for a behavioural health visit is submitted to the patient's medical plan and returns CO-109 — not covered by this payer or contractor. The plan carves behavioural health out to a separate managed behavioural health organisation with its own payer ID.
The patient's card shows the medical plan's name and logo, and often shows the carve-out administrator only in small print on the reverse, if at all.
The claim has to be resubmitted to the correct entity, and the filing deadline has been running from the date of service throughout. A claim that spends two months at the wrong payer arrives at the right one with two months less runway.
What sits behind it
CO-109 means the claim reached an entity with no responsibility for it. The three dominant causes are behavioural health carve-outs, Medicare Advantage plans billed as traditional Medicare, and Medicaid managed care plans billed to the state.
The Medicare Advantage case is particularly costly because it is easy to miss. A patient with a Medicare Advantage plan is not covered by traditional Medicare at all, and claims sent there deny — but the patient will often describe themselves simply as having Medicare.
The prevention is verifying the actual administering entity at eligibility check rather than reading the card. Electronic verification returns which payer is genuinely responsible, including carve-outs and managed care assignments that the card does not disclose.
Related codes
Terms used here — Eligibility Verification · Timely Filing · Coordination of Benefits
How we handle it — Eligibility Verification · Claims Management · Denial Management
Primary sources
The rules behind CO-109, at the bodies that publish them.
- Find your Medicare Administrative Contractor (opens in a new tab)
Centers for Medicare & Medicaid Services — Which MAC processes your Part B claims, by state. Local Coverage Determinations vary by MAC, so this determines which medical necessity policies apply to you.
- Medicare Secondary Payer Manual (opens in a new tab)
Centers for Medicare & Medicaid Services — When Medicare pays second, and to whom the claim goes first. Coordination-of-benefits denials are resolved here rather than with the patient.
- State Medicaid program overviews (opens in a new tab)
Medicaid.gov — Program structure, delivery model and waivers by state. Our state pages summarise the program name and delivery model; this is the authoritative source behind them.
Every denial code with a guide
Authorization
Bundling
Contractual
Coverage
Data quality
Documentation
Eligibility
Liability and workers comp
Patient responsibility
Provider eligibility
Timely filing
Looking for a different code? Search all 190 CARC and RARC codes
Questions about CO-109
The claim went to an entity with no responsibility for it. The three dominant causes are behavioural health carved out to a separate administrator, Medicare Advantage plans billed as traditional Medicare, and Medicaid managed care plans billed to the state rather than the assigned plan.
Because carve-out arrangements frequently are not disclosed on the card, or appear only in small print on the reverse. The card shows the plan the patient recognises, not necessarily the entity that adjudicates a given service type.
Yes, and this is the expensive part. The deadline runs from the date of service throughout, so time spent at the wrong payer is consumed from the correct payer's window. Resubmit promptly rather than treating it as routine rework.
Verify the actual administering entity at eligibility check rather than reading the card. Electronic verification returns which payer is genuinely responsible, including carve-outs and managed care assignments the card does not disclose.
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