(1) Penalty. Upon a failure to pay the entire tax when due, the director shall add a penalty of 15 percent of the tax or unpaid portion thereof, on the first day of each month following the date the tax was due; provided, however, no penalty shall be assessed in excess of 50 percent of the tax due. For the purposes of this title, a payment made by mail shall be deemed received on the date shown on a postage cancellation stamp imprinted on the envelope in which the payment is received, or if payment is made by means other than the United States mail, payment shall be deemed received on the date the payment is stamped “received” by the director.

(2) Interest. On the first day of the month following the date on which the maximum penalty provided for in this section has accrued, interest at the rate of one-half of one percent per month shall begin to accrue. Interest shall accrue at this rate on the amount of the unpaid tax, exclusive of penalties, for each month or portion of a month until the tax is paid. (Ord. 505 § 1. 2002 Code § 6-5.1).