It sounds like you're doing what you're doing in an effort to accommodate the cascading tax calculations necessary for your products. Considering all you've said, I once again recommend touching base with an accountant about these matters to figure out the best way to do this. Sales tax can be assigned to items in inventory when you purchase and sell them, but if the program isn't quite doing what you need it to with the cascading tax, then you may be able to work out alternate solutions. Take a look at the Set up sales tax in QuickBooks Desktop and associated articles to learn more about the sales tax feature in the program.