A Supplemental Property Tax Bill is essentially the difference between the new value of a recently purchased home and the old value of the home. Unlike standard property taxes, which must be paid every year, the supplemental property tax is a one-time tax. Therefore, once you pay the tax, you will not be subjected to further supplemental taxes unless you buy a new house or do additional home construction. The January 1 value is multiplied by a proration factor. The proration factor is the percentage of months remaining in the fiscal year. This result is then multiplied by the tax rate (usually 1% plus voter approved indebtedness) to determine the supplemental tax amount due. If this date occurs between January 1st and May 31st, you will be issued two supplemental tax bills. One is for the remainder of the year and the other is for the fiscal year that follows. If this date occurs between June 1st and December 31st, you will receive one supplemental tax bill that covers the fiscal year following the sale or construction completion date.