Sublet items refer to work that you bill to your customer but you pay another company to do, such as towing or machine shop work.
As such, it has some characteristics of labor items, that is, it is usually a service, but may include deliverable goods, and also some characteristics of parts, such as the requirement to track the service vendor.
Tax on sublet is set up separately from both labor and parts. So sublet may also be useful for handling special fees such as inspection certificates and other charges that may require different tax treatment than both parts or labor.
Use of sublet is not required. Many programs do not even make it available as a third type of line item.
As you can see below, sublet functions are more limited than parts but similar, as described on the Parts and Parts Details pages.
Initial window from a shop with many sublet items:
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