The alternative fuel mixture credit is a tax credit available to taxpayers who use alternative fuels in place of taxable fuels. In Form 720, this credit is claimed on Part IV, Line 11. The credit amount is calculated based on the percentage of alternative fuel used in the mixture and the applicable tax rate. For example, if you used a 20% biodiesel blend in diesel fuel, you would calculate the credit based on 20% of the tax paid on the diesel fuel.