Section 51.807 - Computing Amount of Advance Cash Payment(a) In order to compute the full amount of an advance cash payment, the interest rate on the bonds shall be applied on an annual basis to each unpaid installment of taxes for the number of years the installment of taxes must run before being due. The total of the items computed shall be deducted from the face amount of the unpaid installments of taxes.(b) In order to compute the full amount of an advance cash payment, the interest rate on the bonds shall be applied on an annual basis to each unpaid past-due installment of taxes for the number of years the installment has been past due, and 10 percent of the face amount of each installment that is past due shall be added as a penalty. The total of the items computed shall be added to the unpaid installments. Acts 1971, 62nd Leg., p. 382, ch. 58, Sec. 1, eff. 8/30/1971.