If a vendor fails to pay the tax imposed by this Part 2 when due, the vendor must pay to the Director, in addition to the tax due: interest at the rate of 1% for each month or part of a month that the tax is overdue; and a penalty of 10% of the amount of the tax due. City Code, 1976/83, art. 28, §56A(f) Ord. 99-441 Ord. 04-728