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CO-D1 Denial Code (Deactivated): Subluxation Level Missing

CO-D1 meant the claim was denied because the level of subluxation was missing or inadequate. X12 deactivated it, and its notes tell payers to use CARC 16 with remark codes as needed, such as M122.

X12 deactivated CARCD1 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.

Code: CO-D1 (CARC D1)
Status: Deactivated StoppedOctober 16, 2003 (in use since January 1, 1995).
Code set: Claim Adjustment Reason Codes (CARC)
Group codes: CO (Contractual Obligation): Missing claim information is the provider's to correct, so the patient was not billed.
Official description: Claim/service denied. Level of subluxation is missing or inadequate.
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified: September 24, 2026 against the official X12 list.

What CO-D1 meant

CARC D1 was a chiropractic denial. Payers that cover spinal manipulation expect the claim to identify the level of subluxation being treated. If that detail was left off, or was too vague to support the service, the claim was denied with this code.

What replaced it

X12’s note says to use code 16 and remark codes if necessary. So today the same denial usually appears as CO-16, meaning the claim lacks information, paired with remark code M122, which specifically flags a missing, incomplete, or invalid level of subluxation. Related documentation issues for chiropractic claims include M1 about the timing of x-rays.

If you still see CO-D1

It is a retired code, so it should only surface in long-archived chiropractic claims. For a current subluxation denial, open the visit note and confirm that it documents the spinal level treated and that the claim’s diagnosis codes reflect it. Correct the claim, then resubmit following the payer’s corrected-claim rules. A template that prompts for the treated levels at every visit prevents most of these denials.

CO-16 (Claim/service lacks information or has submission/billing error(s).): The replacement X12 names: claim lacks information or has billing errors, with a remark code.
M122 (Missing/incomplete/invalid level of subluxation.): Remark code for a missing, incomplete, or invalid level of subluxation.
M1 (X-ray not taken within the past 12 months or near enough to the start of treatment.): Remark code when an x-ray was not taken within the required timeframe.

CO-D1 FAQ

Who usually received CO-D1?

Chiropractors billing spinal manipulation, since payers such as Medicare cover manipulation only to treat a documented subluxation at specific spinal levels.

What does a complete subluxation diagnosis include?

Payer requirements vary, but typically the specific spinal region or level treated, reported with a diagnosis coded to the required specificity and supported in the record.

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