Professional service undertaking.
(ii) Professional service undertaking. For purposes of this paragraph (h), an undertaking is treated as a professional service undertaking for any taxable year in which the undertaking derives more than 50 percent of its gross income from the provision of services that are treated, for purposes of section 448 (d)(2)(A) and the regulations thereunder, as services performed in the fields of health, law, engineering, architecture, accounting, actuarial science, performing arts, or consulting.