75 Pa.C.S. § 9613

When any motor carrier fails to file a report and pay the tax within the time prescribed by this chapter for the filing and payment thereof, he shall pay as a penalty for each failure to file or to pay on or before the prescribed date a sum equivalent to 10% of the tax or $50, whichever is greater. In addition to this penalty, any unpaid tax shall bear interest at the rate of 1% per month or fraction thereof until the tax is paid. The penalties and interest charges imposed shall be paid to the department in addition to the tax due.