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CO-46 Denial Code (Deactivated): Service Not Covered

CO-46 meant the service billed was not covered by the plan. X12 deactivated it and its notes direct payers to use CARC 96, non-covered charges, which requires a remark code explaining the reason.

X12 deactivated CARC46 on October 16, 2003. Payers should no longer use it on new remittances, but it can still appear on older ERAs, corrected claims, and appeals.

Quick facts

Code
CO-46 (CARC 46)
Status
Deactivated StoppedOctober 16, 2003 (in use since January 1, 1995).
Code set
Claim Adjustment Reason Codes (CARC)
Group codes
  • CO (Contractual Obligation): The provider absorbed the non-covered amount, for example when no valid advance notice was obtained.
  • PR (Patient Responsibility): The patient could be billed, for example when the plan excludes the service and the patient accepted financial responsibility.
Official description
This (these) service(s) is (are) not covered.
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What CO-46 meant

CARC 46 was a blunt non-coverage denial: “this service is not covered.” It did not say whether the service was excluded by the plan, not medically necessary, experimental, or limited by frequency. It simply told the provider the plan would not pay for it.

What replaced it

X12’s note on this code says to use code 96, so CO-96 is the direct successor. The newer code requires at least one remark code, which gives billers the reason that code 46 left out.

When the reason is more specific, payers use other active codes, such as PR-204 for services outside the current benefit plan or CO-50 for medical necessity.

If you still see CO-46

It is a long-retired code, so it should only appear in historical data. If a payer still sends it, ask them for the remark code or benefit provision behind it.

Resolve the underlying claim as you would a CO-96. Check the patient’s benefits for the service on that date, confirm the diagnosis supports it, and review whether a signed advance notice or financial waiver is on file. With a valid waiver, the patient may be billed; without one, the amount is usually a write-off unless an appeal shows the service is in fact covered.

  • CO-96 (Non-covered charge(s).): The replacement X12 names for this code.
  • PR-204 (This service/equipment/drug is not covered under the patient's current benefit plan): The service, equipment, or drug is not covered under the patient's current benefit plan.
  • CO-50 (These are non-covered services because this is not deemed a 'medical necessity' by the payer.): Not covered because the payer deems it not medically necessary.

CO-46 FAQ

Is CO-46 the same as CO-96?

They describe the same outcome. X12 retired 46 and told payers to use 96, which adds a requirement to include a remark code explaining why the charge is not covered.

Who pays for a service that was not covered?

It depends on the group code and on whether the patient agreed in advance to pay. Under CO, the provider generally writes it off. Under PR, the patient may be billed.