Materials used in repairing, for taxing purposes, fall into the following classes:
In all instances materials are taxable when sold to repairmen for use in making repairs where such materials lose their identity as a result of such use. For instance, solder used in welding, paint used in automobile refinishing, thread used in mending clothing, cloth used in reupholstering. In all instances where the shape or composition of the repair material is materially changed, such altered or changed material is considered to have been used or consumed by the repairman, and, for that reason, subject to tax when sold to him. No tax on this material is to be collected by the repairman from his customer.
In instances where repair materials and repair parts are passed to the repairman's customers without change, except necessary and customary minor adjustments, such parts or materials may be purchased at wholesale by the repairman licensed under the law. The repairman is then liable for sales tax on such sales of materials and parts to his customers.
S.C. Code Regs. § 117-306