If any person subject to this chapter fails to pay any tax required by this chapter within thirty (30) days after the due date thereof, there shall be added to such tax, a penalty of ten percent (10%) of the amount of such tax, and any tax due under this chapter and unpaid, and all penalties thereon, shall constitute a debt to the city, and may be collected by court proceedings, which remedy shall be in addition to all other remedies. (1973 Code § 3.08.070)