Shop supplies charge

Every job uses things nobody bills by the piece. The shop supplies charge is the line that pays for them, and because it is a charge the customer did not ask for by name, it is the line that draws questions at the counter.

Three choices define it: the base (labor only, or labor and parts), the percentage, and the cap. A shop supplies charge computed on labor rises with the hours and not with the parts, so a four-hour job with one gasket pays more of it than a one-hour job with a $900 module. As an example only, 8% of a $300 labor charge is $24, and a $35 cap would not bite until the labor passed $437.50.

Whatever the choice, it is its own line, named for what it is, on the estimate as well as the invoice. Michigan's act asks for a written estimate that "itemizes as closely as possible the price for labor and parts" (MCL 257.1332(1)), and a charge that first appears on the invoice is the kind of surprise that rule exists to stop; the rules pages have each state's words. An environmental or disposal fee, where a state sets one, is a different line with its own basis.

The charge is part of the labor side of the ticket when a shop works out its effective labor rate only if the shop counts it that way; most do not, and the calculator leaves it out.