CO-11: diagnosis inconsistent with the procedure.

What X12 says CARC 11 means

The diagnosis is inconsistent with the procedure.

CARC 11 · Start 01/01/1995, last modified 07/01/2017.

X12 usage note: Refer to the 835 Healthcare Policy Identification Segment (loop 2110 Service Payment Information REF), if present.

In plain terms: The payer says the diagnosis on the claim does not support the procedure billed. Check the diagnosis pointer and the procedure code.

What it means on a remittance

The wording is short and the payer decides what counts as consistent. In practice a payer compares the procedure code with the diagnosis codes it can see on the line and with its own coverage edits. When the pairing falls outside those edits, the line comes back with CARC 11. The X12 usage note points to the 835 policy segment, which, when the payer fills it in, names the policy it applied.

Typical causes

• The diagnosis pointer on the service line points to the wrong diagnosis, or to none.
• A typing or transposition error in an ICD-10-CM code, or a code that is invalid for the date of service.
• A non-specific or unrelated diagnosis listed first, so the line that carries the procedure does not show the supporting diagnosis.
• The payer's coverage policy lists specific diagnoses for the procedure, and the claim shows none of them. Remark code N115 or N569 may point to this.

These are common billing patterns, not a diagnosis of your claim. The remittance and the payer's policy decide.

What to check

1. Open the claim and read the diagnosis pointers for the denied line, not just the claim-level diagnosis list.
2. Confirm each ICD-10-CM code against the record. The ICD-10-CM code search shows the code descriptions.
3. Confirm the procedure code and modifiers with the HCPCS Level II search for Level II codes.
4. Find the payer's policy. For Medicare, an LCD or NCD can be searched at the Medicare Coverage Database.

Correct, resubmit or appeal

If the claim carried a coding or pointer error, correct it and submit a corrected claim the way the payer requires. If the codes are right and the record supports them, ask for review: for Medicare that is a redetermination, filed within 120 days of receiving the notice (receipt is presumed 5 days after the notice date). Attach the part of the record that shows the diagnosis was documented for that service. Non-Medicare payers set their own appeal windows in the contract or plan documents, so read the notice for the date.

Medicare dates that apply

Medicare claims must be filed no later than the close of the period ending 1 calendar year after the date of service (42 CFR 424.44(a)(1)), with exceptions in 424.44(b). A redetermination request must be filed within 120 calendar days from the date a party receives the notice, receipt is presumed 5 days after the notice date (42 CFR 405.942(a)), and a late request can be considered for good cause (405.942(b)). Clerical errors, including inaccurate data entry, are handled by the contractor as reopenings instead of redeterminations (42 CFR 405.980(a)(3)). The tool above runs the date math.

Related codes

X12 does not publish a table that pairs each CARC with remark codes; the payer picks the remark code and prints it beside the CARC on the same remittance line. These X12 remark codes carry wording that speaks to this reason, so look for them:

• MA63 — Missing/incomplete/invalid principal diagnosis.
• M76 — Missing/incomplete/invalid diagnosis or condition.
• N569 — Not covered when performed for the reported diagnosis.
• N115 — This decision was based on a Local Coverage Determination (LCD). An LCD provides a guide to assist in determining whether a particular item or service is covered. A copy of this policy is available at www.cms.gov/mcd, or if you do not have web access, you may contact the contractor to request a copy of the LCD.

Other codes: CARC 50 (medical necessity denials), CARC 4 (modifier does not fit the procedure). The full lookup reads any code on this page.

Worked example (hypothetical)

A line for a procedure comes back CO-11. The pointer on that line was set to diagnosis 3, a general code, instead of diagnosis 1, the condition the procedure treated. The biller fixes the pointer, submits a corrected claim, and records the date. No appeal is filed because the record was never in question.

Sources

• X12: Claim Adjustment Reason Codes — code text, usage notes and dates (list dated 10/30/2026, retrieved 2026-11-02)
• X12: Remittance Advice Remark Codes — remark code text (retrieved 2026-11-02)
• 42 CFR 424.44, 42 CFR 405.942 and 42 CFR 405.980 — eCFR, current through 2026-10-29 (retrieved 2026-11-02)

Code descriptions are X12 copyrighted material, quoted here only for the codes on this page and linked to the owner. For the full lists, use X12. Every rule above was read from these pages on November 2, 2026. Payers revise code lists, contracts and policies, so confirm anything that affects a claim or a deadline with the payer.