71 Pa. Stat. § 1026
Whenever under any act of Assembly the right to practice any profession or work at any trade or occupation is conditioned upon the annual renewal of any license or registration granted by the Department of Public Instruction, for which renewals a fee is prescribed and required to be paid, the department shall, before issuing any such renewal license or certificate of registration, collect from the person licensed or registered, in addition to the fee for the current year, the full amount of all fees and penalties for preceding years which the applicant for renewal has theretofore failed to pay: Provided, That if in any case the applicant proves to the satisfaction of the department that he actually has not practiced such profession or worked at such trade or occupation at any time during any such preceding year or years, then the fee for such year or years shall not be collected.
71 P.S. § 1026