LaboratoryLow audit riskHCPCS

HCPCS Modifier QW

CLIA Waived Test

Source: AMA CPT / CMS HCPCS Level II definitions. Maintained by the D3rx Clinical Billing Team.

What modifier QW means

Modifier QW identifies a laboratory test as CLIA-waived, certifying both that the test appears on the CMS-approved waived-test list and that the laboratory holds a valid CLIA certificate of waiver. Many waived tests must carry QW to be paid.

When to use it

Performing a CLIA-waived test — such as a rapid strep test, urine dipstick, or waived glucose monitoring — under a valid certificate of waiver.

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Documentation checklist

The record should support every item below before you append modifier QW.

  • The laboratory's CLIA certificate number and type
  • That the specific test is on the CMS waived-test list
  • The test date and result

Do NOT use modifier QW when

  • The test is not on the CMS list of waived tests
  • The test is intrinsically waived and the payer does not require QW (a small set of codes never need it)
  • The test is of moderate or high complexity

Common denial reasons

  • QW omitted on a waived test that requires it
  • The lab's CLIA certificate is invalid or expired
  • The test billed is not actually a waived test

Denial codes you may see with modifier QW

CO-18CO-151CO-16

How to appeal a modifier QW denial

Verify the test is on the CMS waived list with a current CLIA certificate, then resubmit with QW and the certificate number. If denied as not-waived, confirm the exact CPT/HCPCS code matches the waived-test list entry for that date of service.

Payer notes

CMS publishes the list of tests that require QW; a handful of waived tests do not need the modifier at all. The billing provider must hold a current CLIA certificate of waiver for the date of service.

Related & commonly confused modifiers

Modifier 91

Where modifier QW is used

  • Waived lab tests (e.g., 81002/81003 urinalysis, rapid strep, waived glucose)
  • Point-of-care/rapid diagnostic tests

Look up these codes & their 2026 Medicare rates

8100281003

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Medical billing disclaimer

Modifier definitions follow standard AMA CPT and CMS HCPCS Level II guidance and are for educational reference. Payer policies, billing formats, and coverage rules vary and change. Always verify the current rule with the specific payer before submitting. D3rx is not responsible for claim outcomes.