CO-275 denial code
Prior payer's patient responsibility not covered
How to fix it
Bill the patient for the remaining responsibility where permitted.
How to prevent it
Set expectations with patients holding secondary coverage that does not absorb all cost sharing.
In practice
A patient holds a secondary policy and the practice bills it for the deductible left by the primary. The secondary returns CO-275, declining to cover the primary's patient responsibility.
Not every secondary policy absorbs cost sharing. Some cover only services the primary denied, some apply their own deductible first, and some exclude the primary's patient responsibility entirely.
Confirm what the secondary actually covers, then bill the patient for what remains. Setting that expectation before the service is considerably better than explaining it after a bill arrives.
What sits behind it
Patients holding two policies commonly assume the second eliminates their out-of-pocket cost, and that assumption is frequently wrong. True supplemental coverage designed to absorb cost sharing is a specific product, not a general property of having secondary insurance.
The distinction matters at verification. Reading what the secondary covers rather than confirming it exists is what allows the practice to tell the patient accurately what they will owe, which is the difference between an informed patient and a surprised one.
Where the secondary is a genuine supplement and still declines, check the coordination method. Some plans calculate their liability in ways that produce no payment even where cost sharing exists, and understanding the method explains an otherwise puzzling result.
Related codes
Terms used here — Coordination of Benefits · Patient Responsibility · Allowed Amount
How we handle it — Patient Collections · Eligibility Verification · Patient Support
Primary sources
The rules behind CO-275, at the bodies that publish them.
- Advance Beneficiary Notice of Noncoverage (ABN) (opens in a new tab)
Centers for Medicare & Medicaid Services — The form and the rules for issuing it. Whether a non-covered service can be billed to the patient usually turns on whether a valid ABN was obtained beforehand.
- No Surprises Act guidance (opens in a new tab)
Centers for Medicare & Medicaid Services — Balance billing restrictions, good faith estimates and the independent dispute resolution process — all of which change what a practice may bill a patient.
- 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-275
No. Some secondary policies cover only services the primary denied, some apply their own deductible first, and some exclude the primary's patient responsibility outright. Coverage that absorbs cost sharing is a specific product rather than a general property.
Before the service rather than after. Verifying what the secondary actually covers, not merely that it exists, lets the practice tell the patient accurately what they will owe, which avoids the conversation that follows an unexpected bill.
Often because of the coordination method. Some plans calculate their liability in ways that produce no payment even where cost sharing remains, and understanding which method applies explains a result that otherwise looks like an error.
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