CO-180 denial code
Patient has not met the required residency requirements
How to fix it
Verify the patient's address of record with the plan and correct if wrong.
How to prevent it
Confirm the address on the payer's record matches the patient's actual residence at verification.
In practice
A patient moves across a state line and continues seeing the same physician. Their plan restricts coverage to residents of the prior state, and the claim returns CO-180.
The plan checks the address on its own record rather than the one on the claim. A patient who moved without notifying the plan will fail a residency test while being perfectly eligible in fact, or the reverse.
Verify the address the plan holds and have the patient update it where it is wrong. Where the move genuinely puts them outside the service area, the question becomes whether the plan covers out-of-area care and on what terms.
What sits behind it
Residency conditions concentrate in geographically defined products: Medicaid managed care, marketplace plans with county-level service areas, regional health maintenance organisations and some employer plans built around a single location.
State Medicaid programs are the strictest, because eligibility itself is state-based. A patient moving between states does not transfer coverage; they must disenrol and apply in the new state, and there is frequently a gap during which no program covers them.
For students, seasonal residents and patients splitting time between addresses, this recurs unless handled deliberately. Many plans have provisions for these situations, but they have to be invoked rather than assumed, and the patient usually has to initiate.
Related codes
Terms used here — Eligibility Verification · Out-of-Network · Coordination of Benefits
How we handle it — Eligibility Verification · Denial Management · Patient Support
Primary sources
The rules behind CO-180, at the bodies that publish them.
- 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.
- Medicare Coverage Database (LCD/NCD) (opens in a new tab)
Centers for Medicare & Medicaid Services — Searchable national and local coverage determinations. The direct answer to whether a diagnosis supports medical necessity for a given procedure.
- Claim Adjustment Reason Codes (CARC) (opens in a new tab)
X12 — The authoritative, maintained CARC list. Our denial code lookup explains these in plain English; X12 is where the canonical definitions live.
Looking for a different code? Search all 190 CARC and RARC codes
Questions about CO-180
The one on its own membership record, not the one on the claim or in your chart. A patient who moved without telling the plan will fail the test despite being eligible, and correcting the plan's record is the only route that resolves it.
No. Eligibility is state-based, so a patient moving states must disenrol and apply in the new one, and there is frequently a gap with no coverage. Claims for services in that gap are rarely recoverable from either state.
Many plans have provisions for patients legitimately residing in two places, but they must be invoked rather than assumed and the patient generally has to initiate. Without that, the pattern recurs on every claim from the secondary address.
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