Our support plans include tier-based percentage discounts on both equipment and labor. Since we always bill actual time for service calls (and because frankly it would take too long with the volume of service calls we perform) we don't create quotes/proposals for service calls. We just go out and bill for the labor/product utilized for that call. We very much need a way to apply discounts to service call invoices. This is also extremely important because we sometimes offer situational discounts to customers for things that don't come up until we are on site, so there's no way to account for them at the quote stage.