The QW Modifier and the Codes That Do Not Need It

For a waiver lab, the QW modifier is the most visible place CLIA shows up in billing. Medicare does not decide from a CPT code alone whether a test was waived. For most waived tests, the code has to arrive with QW attached, and the claim has to come from a lab whose CLIA certificate allows that test.

What does the QW modifier tell Medicare?

That the service was performed with a test system categorized as waived. Medicare's Claims Processing Manual explains the mechanism: "The Food and Drug Administration approves CLIA waived tests on a flow basis. The CMS identifies CLIA waived tests by providing an updated list of waived tests to the A/B MACs (A) and (B) on a quarterly basis via a Recurring Update Notification. To be recognized as a waived test, some CLIA waived tests have unique HCPCS procedure codes and some must have a QW modifier included with the HCPCS code" (Pub. 100-04, Chapter 16, section 70.8).

The notices repeat the same instruction for new codes. The January 2026 notice says: "The Healthcare Common Procedure Coding System (HCPCS) codes for the following new test(s) must have the modifier QW to be recognized as a waived test(s)" (CMS Transmittal 13465, Change Request 14273).

Why does Medicare check the CLIA certificate?

Because it pays only for tests the lab is certified to perform. The waived-test notices carry the same policy line: "To ensure that Medicare and Medicaid only pay for laboratory tests categorized as waived complexity under CLIA in facilities with a CLIA certificate of waiver, laboratory claims are currently edited at the CLIA certificate level."

For nonwaived codes the edit runs the other way. "A facility that submits a claim for any test mentioned in the HCPCS codes that are subject to CLIA edits list must have either a valid, current CLIA certificate of registration (certificate type 9), a CLIA certificate of compliance (certificate type 1), or a CLIA certificate of accreditation (certificate type 3)" (Chapter 16, section 70.9). A waiver lab billing a moderate complexity code is outside its certificate twice: once for CLIA, once for the claim edit.

The certificate number itself rides on the claim. See putting the CLIA number on claims.

Which codes never take the QW modifier?

Nine. The cumulative list of waived tests attached to CMS's change requests begins with them, and the notices say these codes "do not require a QW modifier to be recognized as a waived test" (CMS Transmittal 10397):

These track the original list of waived tests in 42 CFR 493.15(c). For the fecal occult blood codes, the CMS list adds "Contact your Medicare carrier for claims instructions."

Everything else on the waived list takes QW. A few common ones from the CMS list: 81003QW for automated dipstick urinalysis on a waived reader, 82274QW and G0328QW for immunoassay fecal occult blood, 83036QW for hemoglobin A1c on waived analyzers, 85610QW for prothrombin time on waived meters, 86308QW for a mono screen, 87804QW for influenza antigen and 87880QW for strep A antigen.

How do new waived tests reach the claims system?

Through those quarterly Recurring Update Notifications, each titled "New Waived Tests." The most recent one, effective January 1, 2026, added two codes: 87494QW for chlamydia and gonorrhea by multiplex amplified probe and 87812QW for a combined SARS-CoV-2 and influenza A and B antigen test read visually (CMS MLN MM14273). MACs must "permit the use of code 87494QW and 87812QW for claims submitted by facilities with a valid, current CLIA certificate of waiver with dates of service on or after January 1, 2026" (Transmittal 13465). See waived tests new in 2026.

Two details in those notices matter when a claim was denied before the update reached your MAC. First, the effective date "is the date of service." Second, MACs "won't search their files to either retract payment or retroactively pay claims. However, MACs will adjust claims if you bring them to their attention" (MM14273). If a waived test was denied during the gap, ask for the adjustment.

The notices also limit what a MAC may use against you: contractors "shall not use, as a reason for rejecting a claim, the explanatory information found in the FDA Review Decision Summary documentation" for the test (Transmittal 13465).

What about PPM codes?

PPM procedures have their own codes and do not use QW. Medicare's manual lists them, including Q0111 for wet mounts, Q0112 for KOH preparations, Q0113 for pinworm examinations, Q0114 for fern tests, 81015 for microscopic urinalysis and 89055 for fecal leukocytes. A lab with a PPM certificate "may perform only those tests specified as provider-performed microscopy procedures and waived tests" (Chapter 16, section 70.6). See the PPM certificate.

Do other payers use QW?

The QW rules above are Medicare's, and Medicaid is named in the same policy line. Commercial payers and Medicaid managed care plans publish their own policies, and their edits vary. Check each payer's laboratory policy before assuming Medicare's rule carries over.

Who handles which part?

We keep the certificate side right: the correct certificate type for every test you bill, a test menu that matches what you run, and changes reported before you bill anything new. A $149 Readiness Review compares your billed lab codes with your certificate. Claims themselves belong with your biller. Our sister company, White Glove Medical Billing, is a separate company; its post on the denial codes behind most of your money is a good place to start on denials.