Time for payment of taxes, penalties and interest. All taxes, penalties and interest assessed under this chapter, unless earlier payment

§ 9614.  Time for payment of taxes, penalties and interest. All taxes, penalties and interest assessed under this chapter, unless earlier payment is provided in this chapter, shall be paid within 15 days after notice and demand have been mailed to the motor carrier by the department. If the taxes, penalties and interest assessed pursuant to this section and sections 9612 (relating to arbitrary assessment to prevent tax avoidance) and 9613 (relating to penalty and interest for failure to report or pay tax) are not paid within 15 days, there shall be added to the amount of assessment, in addition to interest as already provided and any other penalties provided by law, a sum equivalent to 5% of the tax.