Ind. Code § 6-6-5.5-7.5

Sec. 7.5. Notwithstanding any other provision, the annual excise tax for a motor vehicle, trailer, or semitrailer and tractor operated primarily as a farm truck, farm trailer, or farm semitrailer and tractor as described in IC 9-29-5-13 (before its expiration) or IC 9-18.1-7 is fifty percent (50%) of the amount listed in this chapter for a truck, trailer, or semitrailer and tractor of the same declared gross weight.