Indiana Code Title 6. Taxation § 6-6-1.1-502

(1) Enter the total number of invoiced gallons of gasoline received during the preceding calendar month.

(2) Subtract the number of gallons for which deductions are provided by sections 701 through 705 of this chapter from the number of gallons entered under subdivision (1).

(3) Subtract the number of gallons reported under section 501(3) of this chapter.

(4) Multiply the number of invoiced gallons remaining after making the computation in subdivisions (2) and (3) by the tax rate prescribed by section 201 of this chapter to compute that part of the gasoline tax to be deposited in the highway, road, and street fund under section 802(2) of this chapter or in the motor fuel tax fund under section 802(3) of this chapter.

(5) Multiply the number of gallons subtracted under subdivision (3) by the tax rate prescribed by section 201 of this chapter to compute that part of the gasoline tax to be deposited in the fish and wildlife fund under section 802(1) of this chapter.

(1) estimated monthly gasoline tax liability for the current year;  or

(2) average monthly gasoline tax liability for the preceding year;