A business, trade, profession or occupation, as distinguished from personal services as an employe or casual employe, is carried on partly within and partly without this Commonwealth if one or more of the activities described in § 101.8 (relating to income from sources within this Commonwealth), is systematically and regularly carried on within this Commonwealth and one or more of the activities is systematically and regularly carried on outside of this Commonwealth or if one or more of the activities is systematically and regularly carried on both within and without this Commonwealth.
61 Pa. Code § 109.4
The provisions of this §109.4 amended under section 354 of the Tax Reform Code of 1971 (72 P. S. § 7354).