Question: I'm confused about whether to apply modifier AQ on my claims. If our ZIP code is in the annual file, do I need to use the modifier? Washington Subscriber Answer: If your ZIP code is in Medicare's annual file for automated Health Professional Shortage Area (HPSA) bonus payment, you should not report modifier AQ (Physician providing a service in an unlisted health professional shortage area [HPSA]). Your payer will make the bonus payment automatically. Who uses AQ: Effective Jan. 1, 2009, coders in areas "eligible on December 31 of the prior year for the HPSA bonus but not on the automated ZIP code list" should use modifier AQ to receive the HPSA bonus, according to MLN Matters article MM6106 (www.cms.hhs.gov/mlnmattersarticles/downloads/MM6106.pdf).