The real estate transfer tax imposed under this Article is due and payable at the time of the transfer of the real property, and is delinquent if it remains unpaid for thirty (30) days thereafter. In the event that the tax is not paid prior to becoming delinquent, a delinquency penalty of fifteen percent (15%) of the amount of tax due shall accrue. In the event a portion of the tax is paid prior to becoming delinquent, the penalty shall only accrue as to the portion which is delinquent, and interest shall accrue at the rate of one and one-half percent (1.5%) per month, or fraction thereof, on the amount of tax, exclusive of penalties, from the date the tax becomes delinquent to the date of payment. Interest and penalty accrued shall become part of the tax. (Prior code 3.12.140)