When preparing an estimate, there should be an option to calculate the tax that will be paid to the supplier along with the material order. This ensures that the material cost in the estimate reflects the actual total cost, including tax, rather than just the pre-taxed subtotal of the materials needed. Since this doesn't currently build in the tax we will pay to our supplier, the tax that ultimately is charged on the material list cuts into our profit margin since it wasn't accounted for in the estimate.