All taxes, penalties and interest assessed pursuant to this chapter, unless earlier payment is provided in this chapter, shall be paid within 30 days after notice and demand shall have been mailed to the carrier by the Department of Transportation. If such taxes, penalties, and interest so assessed pursuant to §§ 5216, 5217 and 5218 of this title, shall not be paid within 30 days, there may 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.