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CO-D16 Denial Code (Deactivated): Prior Payer Info Missing

CO-D16 meant the claim lacked the prior payer's payment information, so a secondary payer could not coordinate benefits. X12 deactivated it and its notes say to use CARC 16 with remark code N4.

X12 deactivated CARCD16 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-D16 (CARC D16)
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 primary's payment details; the patient was not billed for the denial.
Official description: Claim lacks prior payer payment information.
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified: September 24, 2026 against the official X12 list.

What CO-D16 meant

When a patient has two plans, the secondary needs to know what the primary did before it can pay. CARC D16 was the secondary payer’s response to a claim that arrived without the primary’s payment information. Without it, the secondary could not calculate its share.

What replaced it

X12’s note is precise: use code 16 with remark code N4. So the modern equivalent is CO-16 paired with N4, meaning the prior insurance carrier’s EOB information is missing, incomplete, or invalid. When a payer thinks another plan should pay first but no primary is listed, it uses OA-22. Correctly reported prior payment then appears on the secondary remittance as OA-23.

If you still see CO-D16

It will only be on old secondary claims. For the same problem now, post the primary’s remittance with all its adjustment codes, confirm your system builds the coordination-of-benefits data into the secondary claim, and verify that line amounts balance. Then resubmit to the secondary, or attach the primary EOB if the payer accepts paper.

CO-16 (Claim/service lacks information or has submission/billing error(s).): Named replacement: claim lacks information.
N4 (Missing/Incomplete/Invalid prior Insurance Carrier(s)): The remark code X12 specifies: missing, incomplete, or invalid prior insurance carrier EOB.
OA-22 (This care may be covered by another payer per coordination of benefits.): The care may be covered by another payer per coordination of benefits.
OA-23 (The impact of prior payer(s) adjudication including payments and/or adjustments. (Use only with Group Code OA)): The impact of prior payer adjudication, shown once the prior payment is reported.

CO-D16 FAQ

What prior payer information does a secondary claim need?

Typically the primary's paid amount, the adjustments with their group and reason codes, and the payment date, sent electronically at the claim or line level, or as an EOB attachment on paper claims.

Why might the information be missing even if I sent it?

Common causes include a primary payment posted without its adjustment detail, line amounts that do not balance, or a clearinghouse edit that dropped the coordination loops. Check the claim file that was actually sent.

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