CARC 133: service line pending further review.

What X12 says CARC 133 means

The disposition of this service line is pending further review. (Use only with Group Code OA).

CARC 133 · Start 07/01/2014, last modified 07/01/2017.

X12 usage note: Use of this code requires a reversal and correction when the service line is finalized (use only in Loop 2110 CAS segment of the 835 or Loop 2430 of the 837).

In plain terms: The line is not finally decided. It is still under review, and the payer will send a reversal and a corrected remittance when it is finalized.

What X12 says about it

The X12 usage text says use of this code requires a reversal and correction when the service line is finalized (use only in Loop 2110 CAS segment of the 835 or Loop 2430 of the 837). In plain terms, this tells you the payer has not decided the line yet.

Typical causes

• The payer is reviewing the line, for example for records or coverage.
• The claim is waiting on information the payer requested.
• The payer applied the code with a group code other than OA, contrary to the X12 note, so ask the payer to confirm the status.

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

What to check

1. Do not post the line as a final denial or write it off yet.
2. Look for a records request or letter from the payer about the line.
3. Watch for a later reversal and corrected remittance for the same claim.
4. Check the claim status with the payer if no follow-up arrives within its usual processing time.

Correct, resubmit or appeal

Wait for the corrected remittance, respond to any information request, and post the final result when it arrives. Appeal clocks usually start from the final determination notice, but confirm the date with the payer.

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: CARC 23, another code X12 limits to Group Code OA, and the full lookup.

Worked example (hypothetical)

A remittance shows OA-133 on one line and a payment on the others. The biller leaves the line open, calls for status after the payer's usual processing time, and posts the corrected remittance when it arrives.

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.