61 Pa. Code § 109.3
A business, trade, profession or occupation, as distinguished from personal services as an employe or casual employe, is carried on by a nonresident wholly within this Commonwealth, if the activities described in § 101.8 (relating to income from sources within this Commonwealth) are carried on solely within this Commonwealth and none of the activities are carried on outside of this Commonwealth though the nonresident or his representative travels outside of this Commonwealth for purpose of buying, selling, financing or performing duties in connection with the business, and even though sales may be made to, or services performed for, or on behalf of, persons or corporations located outside of this Commonwealth. If a nonresident individual carries on a business, trade, profession or occupation wholly within this Commonwealth, all his items of income, gain, loss and deduction attributable to the business shall be deemed from sources within this Commonwealth.
61 Pa. Code § 109.3
The provisions of this §109.3 amended under section 354 of the Tax Reform Code of 1971 (72 P. S. § 7354).
This section cited in 61 Pa. Code § 101.8 (relating to income tax sources within this Commonwealth).