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CO-D20 Denial Code (Deactivated): Service Info Missing

CO-D20 meant the claim or service line was missing service or product information. X12 deactivated it and its notes say to use CARC 16 with the appropriate remark code, such as M51 for procedure codes.

X12 deactivated CARCD20 on June 30, 2007. Payers should no longer use it on new remittances, but it can still appear on older ERAs, corrected claims, and appeals.

Code: CO-D20 (CARC D20)
Status: Deactivated StoppedJune 30, 2007 (in use since January 1, 1995).
Code set: Claim Adjustment Reason Codes (CARC)
Group codes: CO (Contractual Obligation): The provider needed to supply the missing service detail; the patient was not billed.
Official description: Claim/Service missing service/product information.
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified: September 24, 2026 against the official X12 list.

What CO-D20 meant

CARC D20 was a broad “we can’t tell what you provided” denial. The claim or line was missing information that identified the service or product, such as a code, units, or a description. The payer could not price or review the line without it.

What replaced it

X12’s note says to use code 16 with an appropriate remark code. The current form is CO-16, paired with a remark that pinpoints the gap, for example M51 for a missing or invalid procedure code or M53 for missing days or units.

If you still see CO-D20

It should only appear in old remittances. For a current incomplete-service denial, read the remark code, compare the claim line against the charge entry and documentation, and fill in the missing element. If the service used an unlisted or not-otherwise-classified code, add the narrative description the payer requires before resubmitting.

CO-16 (Claim/service lacks information or has submission/billing error(s).): Named replacement: claim lacks information or has billing errors.
M51 (Missing/incomplete/invalid procedure code(s).): Remark code for a missing, incomplete, or invalid procedure code.
M53 (Missing/incomplete/invalid days or units of service.): Remark code for missing, incomplete, or invalid days or units of service.

CO-D20 FAQ

What counts as service or product information?

Anything that identifies what was provided: the procedure or revenue code, units, drug or supply identifiers, and descriptions required for unlisted codes.

How do I learn exactly what is missing?

Read the remark code on the remittance. Under the replacement approach, the remark names the specific missing element.

Important: read before using this information

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