Rev. Rul. 57-259

A single-unit truck, which was put into taxable use on July 1, was subsequently altered so that it could pull a trailer. Likewise, a truck-tractor, which also was put into taxable use on July 1, was subsequently converted to a single unit. In either instance, the alteration changes the classification of the vehicle for purposes of the highway motor vehicle use tax. Held , in accordance with the provisions of section 4481 of the Internal Revenue Code of 1954, tax due for any tax year on the use of a highway motor vehicle is computed on the basis of the taxable gross weight of the vehicle at the time of its first taxable use in that year, and any alteration in the vehicle subsequent to such first taxable use will not affect the tax for that year, even though the alteration changed its classiication under the schedule of taxable gross weights set forth in the regulations. However, liability for the subsequent tax year will be based on the taxable gross weight assigned to the category of the schedule of taxable gross weights in which the vehicle falls at the the time of its first taxable use in that year.