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OA-133 Denial Code: Service Line Pending Review

OA-133 means the disposition of this service line is pending further review. The payer has not made a final decision on the line. X12 requires the payer to send a reversal and correction when the line is finalized, so it is a placeholder, not a denial.

Quick facts

Code
OA-133 (CARC 133)
Status
Active In use since July 1, 2014; last modified July 1, 2017.
Code set
Claim Adjustment Reason Codes (CARC)
Group codes
  • OA (Other Adjustment): The only group allowed. The line is pending with no final liability assigned to either the provider or the patient.
Official description
The disposition of this service line is pending further review. (Use only with Group Code OA). Usage: 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).
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What OA-133 means

CARC 133 says the disposition of this service line is pending further review. X12 restricts it to group code OA and to the service line level (loop 2110 of the 835). It is a holding code: the payer processed the rest of the claim but set this line aside for more review.

The usage note is important. Using CARC 133 requires the payer to send a reversal and correction once the line is finalized. In other words, a later remittance will reverse the pending line and replace it with the final decision, which could be a payment, a denial, or an adjustment.

Example: a claim with three lines pays two of them. The third shows OA-133 with no payment. Several weeks later, a new ERA reverses that line and reports it as paid.

Common causes

  • Clinical or coding review of a specific service, such as a high-cost drug or unusual procedure.
  • A records request or pre-payment review affecting only that line.
  • Pending pricing, for example for an unlisted code or an item that needs manual pricing.
  • A coordination of benefits or eligibility question tied to that service.

How to fix it

  1. Do not resubmit or appeal yet. The line has not been decided, and resubmitting may lead to a duplicate claim denial.
  2. Check for records requests. If the payer asked for documentation, send it promptly.
  3. Post the line as pending in your system, not as a denial or a write-off.
  4. Follow up if the reversal and correction does not arrive within the payer’s usual timeframe. Ask provider services what is holding the line.
  5. Act on the final decision when it arrives: post payment, appeal a denial, or bill patient responsibility as applicable.

How to prevent problems with OA-133

  • Set up a pending status for OA-133 lines so they stay on a work list until finalized.
  • Respond to documentation requests quickly to shorten reviews.
  • For unlisted or manually priced services, include a clear description and supporting documents with the original claim.
  • Track pending lines by payer with an ERA Analyzer so long-running reviews are visible.
  • For how pending, rejected, and denied claims differ, see claim rejection vs. denial.
  • OA-257 (The disposition of the claim/service is undetermined during the premium payment grace period, per Health Insurance Exchange requirements.): A pending status used during a Health Insurance Exchange premium grace period, also later reversed and corrected.
  • OA-277 (The disposition of the claim/service is undetermined during the premium payment grace period, per Health Insurance SHOP Exchange requirements.): The same grace-period hold for coverage purchased through a SHOP Exchange.
  • CO-252 (An attachment/other documentation is required to adjudicate this claim/service.): An attachment or other documentation is required to adjudicate the claim.
  • CO-101 (Predetermination: anticipated payment upon completion of services or claim adjudication.): Predetermination, another non-final result.

OA-133 FAQ

Should I resubmit a line with OA-133?

No. Resubmitting can create a duplicate. The payer is still reviewing the line and will send a reversal and correction when it is finalized.

Can I bill the patient while OA-133 is pending?

No. There is no final patient responsibility yet. Wait for the final adjudication.

How long does a pending review take?

It depends on the payer and the type of review. If the line stays pending longer than the payer's normal timeframe, follow up with provider services.