Sec. 5. As used in this chapter, "taxpayer" means an individual who:
(1) is a physician engaged in the practice of medicine;
(2) has an ownership interest in a corporation, limited liability company, partnership, or other legal entity organized to provide health care services as a physician owned entity;
(3) is not employed by a health system (as defined in IC 16-18-2-168.5); and
(4) has any state income tax liability.