72 Pa. Stat. § 3988
All bonds, issued under the authority of this act, shall be redeemed at maturity, and all interest, due from time to time on such bonds, shall be paid by the Board of Finance and Revenue of the Treasury Department of the Commonwealth. For the specific purposes of redeeming said bonds at maturity and paying all interest thereon, and, in accordance with the information received from the Governor as provided in section seven of this act, the General Assembly shall biennially appropriate, out of the Motor License Fund, the moneys necessary for the payment of the interest on said bonds and the principal thereof at maturity: Provided, however, That, if at any time the said Motor License Fund shall be abolished; or, if at any time the amount in said Motor License Fund shall be insufficient to enable the General Assembly to make the appropriation, required by this act out of said Motor License Fund, the General Assembly shall make such appropriation out of any other available fund, or funds, in the State Treasury. All moneys so appropriated shall be paid into the sinking fund by the State Treasurer, and all such moneys, not necessary to pay accruing interest, shall be invested by the Board of Finance and Revenue in such securities as are provided by law for the investment of the sinking funds of the Commonwealth.
The investments and moneys and the accumulations thereon in the sinking fund shall be devoted to, and be used exclusively for, the payment of the interest accruing on such bonds and their redemption at maturity: Provided, however, That the Board of Finance and Revenue is authorized, at any time, to use any of such funds for the purchase and retirement, at not more than par, of all, or any part of, the bonds issued under the authority of this act. In the event that all, or any part of, said bonds shall be purchased by the Board of Finance and Revenue, they shall be cancelled and returned unto the State Treasurer as cancelled and paid bonds; and thereafter all payments of interest thereon shall cease; and the cancelled bonds and coupons shall be destroyed within two years after cancellation, in the presence of the Governor, the Auditor General, and the State Treasurer; and a certificate evidencing the destruction, satisfactory to the duly authorized loan and transfer agent of the Commonwealth, shall be furnished to it. All cancelled bonds and coupons shall be so marked as to make the cancelled bonds and coupons non-negotiable.
72 P.S. § 3988