Ill. Admin. Code tit. 86 § 140.120
Any person who sells tangible personal property as an incident to a sale of service is a serviceman who is engaged in the business of making sales of service within the meaning of the Act and upon whom a tax is imposed under the Act. Among other things, the term "serviceman" includes a person who repairs tangible personal property for users, except that this is not true when a railroad, on a nonprofit basis, repairs cars for another railroad at an interchange point in connection with the interchange of traffic. Such repair activities by one railroad for another at interchange points in connection with the interchange of traffic do not constitute a business of making sales of service within the meaning of the Service Occupation Tax Act. For sales of service in which the cost price of tangible personal property transferred is less than 35% of the gross selling price, see Section 140.101 of this Part.
Ill. Admin. Code tit. 86, § 140.120
Amended at 14 Ill. Reg. 262, effective January 1, 1990