CO-182: procedure modifier invalid on the date of service.

What X12 says CARC 182 means

Procedure modifier was invalid on the date of service.

CARC 182 · Start 06/30/2005, last modified 09/30/2007.

In plain terms: A modifier on the line was not a valid code on the date of service.

What it means on a remittance

Modifiers come and go from code sets. A modifier that is valid in one year can be retired or replaced in another, and the payer checks the modifier against the code set in force on the date of service.

Typical causes

• The modifier was retired or not yet in effect on the date of service.
• A typing error produced a modifier that never existed.
• The claim reused a modifier from an older template.

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

What to check

1. Compare the modifier against the code set for the date of service. The HCPCS Level II search covers Level II modifiers.
2. Check the payer's modifier guidance for the year.
3. Look at the line's remark code for more detail.

Correct, resubmit or appeal

Correct the modifier and submit a corrected claim as the payer requires. If the modifier was valid on that date and the payer rejected it, ask for review and cite the code-set source you relied on. For Medicare, a redetermination is filed within 120 days of receiving the notice.

Medicare dates that apply

A Medicare redetermination request must be filed within 120 calendar days from the date a party receives the notice of the initial determination; receipt is presumed 5 calendar days after the notice date unless there is evidence to the contrary (42 CFR 405.942(a)), and a late request can be considered for good cause (405.942(b)). Other payers set their own appeal windows in the contract or plan documents, so read the notice for the date. The tool above runs the date math.

Related codes

Other codes: Compare CARC 4 (modifier does not fit the procedure), modifier 25 and modifier 59.

Worked example (hypothetical)

A line is denied CO-182 because the biller used a modifier from a prior year's template that was retired before the date of service. The biller removes it, adds the current modifier, and submits a corrected claim.

Sources

• X12: Claim Adjustment Reason Codes — code text, usage notes and dates (list dated 10/30/2026, retrieved 2026-11-02)
• 42 CFR 405.942 — 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. The X12 text and the Medicare rule above were read from these pages on November 2, 2026. Causes, checks and examples are general billing practice written for this page, not X12 content. Payers revise code lists, contracts and policies, so confirm anything that affects a claim or a deadline with the payer.