Rebate on advance payments: credit for advance gift-tax payments plus a capped additional proportional credit at assessment. A rebate on advance payments allows a donor who pays part of the gift tax into the treasury within fifteen days to receive at assessment credit for the amount paid and an additional proportional credit equal to one-ninth of that payment, subject to a cap that the additional credit not exceed one-tenth of the tax due. For multiple gifts in a year, the tax attributable to any single gift is the difference between tax on the aggregate including the gift and tax on the aggregate excluding it, under the applicable computation method.