Caterpillar Tractor Co. v. Lenckos

The plaintiffs, Caterpillar Tractor Company and four of its corporate subsidiaries, filed separate Illinois corporate income tax returns for 1969 through 1974 inclusive. Each corporation, whose business income is generated through multistate and multinational business operations, in preparing its return applied the apportionment formula set out in section 304(a) of the Illinois Income Tax Act (Ill. Rev. Stat. 1969, ch. 120, par. 3 — 304(a)) for the use of corporations deriving business income from transactions in Illinois and in one or more other States. A purpose of the apportionment formula…