72 Pa. Stat. § 7238
Notwithstanding the provisions of clause (1) of subsection (b) of section 237 of this article, tax due on the sale at retail or use of a motor vehicle, trailer or semi-trailer, except mobilehomes as defined in "The Vehicle Code," required by law to be registered with the department under the provisions of "The Vehicle Code" shall be paid by the purchaser or user directly to the department upon application to the department for an issuance of a certificate of title upon such motor vehicle, trailer or semi-trailer. The department shall not issue a certificate of title until the tax has been paid or evidence satisfactory to the department has been given to establish that tax is not due. The department may cancel or suspend any record of certificate of title or registration of a motor vehicle, trailer or semi-trailer when the check received in payment of the tax on such vehicle is not paid upon demand. Such tax shall be considered as a first encumbrance against such vehicle and the vehicle may not be transferred without first payment in full of such tax and any interest additions or penalties which shall accrue thereon in accordance with this article.
72 P.S. § 7238