RARC M12: Diagnostic Tests Missing Purchased Service Indicator

What Does RARC M12 Mean?

When you see M12 on your remittance, the payer is telling you that the claim includes diagnostic tests but lacks the information needed to determine where those tests were actually performed. Payers require this distinction because reimbursement rates and billing rules differ depending on whether a provider ran the test in their own facility or purchased the results from an external laboratory or diagnostic center.

This remark typically appears alongside CARC codes that flag missing or invalid claim data, such as CARC 4 or CARC 16. The payer's system could not adjudicate the claim because the purchased service modifier — commonly modifier 90 for purchased lab tests or modifier TC/26 for technical and professional components — was either absent or improperly applied. In some cases, the purchased service indicator in the claim form's designated field was left blank.

It is worth noting that this code usually points to a straightforward documentation gap rather than a clinical or coverage dispute. However, if the underlying diagnostic test itself has coverage limitations or the purchased service arrangement does not meet the payer's network or certification requirements, additional issues may surface once the indicator is added and the claim is reprocessed.

What to Do

Review the claim to determine whether the diagnostic tests were performed in your office or purchased from an outside provider. If the tests were purchased, append modifier 90 to the applicable procedure codes. For radiology or other technical services, ensure the appropriate TC (technical component) or 26 (professional component) modifier is in place. If the test was performed in-house, confirm the claim does not inadvertently suggest otherwise and that the purchased service indicator field is properly marked.

Once the correct modifier or indicator is applied, resubmit the claim as a corrected claim using the appropriate frequency code. Going forward, build the purchased service check into your charge entry workflow so that any diagnostic test ordered from an outside facility automatically triggers the correct modifier at the point of billing.

Common Scenarios

• A physician orders bloodwork that is drawn in the office but sent to a reference laboratory for processing — the claim is submitted without modifier 90, triggering M12 because the payer cannot tell who actually performed the analysis.
• A clinic purchases portable X-ray services from a mobile imaging company and bills the payer for the diagnostic study, but omits the purchased service indicator, causing the payer to reject the claim for missing information.
• A group practice performs EKGs in-house but the billing template defaults to leaving the purchased service field blank, resulting in M12 on multiple remittance advices until the template is corrected.

Commonly Paired With

RARC M12 commonly appears alongside these CARC denial codes: