77 Pa. Stat. § 2618
Each subscriber to the fund shall, within one (1) month after his subscription has terminated, furnish a written statement to the board setting forth the maximum average and minimum number of employes insured in the fund that such subscriber had employed during the preceding year, and the actual amount of the money payroll of such employes for such year. When the board has subdivided the employments in any group into classes, as provided in section 1510 , the subscriber shall state the number and actual amounts of the money payroll of such employes of each of such classes. Within thirty (30) days, the board shall state the account of each subscriber for that year, based on the facts thus proven, and shall render a copy of this statement to the subscriber. If the amount of the premium theretofore paid by a subscriber shall exceed the amount due according to such stated account, then the excess shall be forthwith refunded to the subscriber by payment out of the fund. If the amount shown by the statement exceeds the amount of the premium theretofore paid by the subscriber, the excess shall be forthwith due and payable by the subscriber into the fund, and until paid shall be a lien, as State taxes are a lien, upon the real and personal property of the subscriber, and, if unpaid, shall be collectible as State taxes are now collectible, with interest at the rate of twelve per centum per annum commencing thirty (30) days after service of the copy of the account, which service shall be by registered mail.
77 P.S. § 2618