Q. How can I make Peachtree calculate sales tax for construction projects where only a percent of the total is taxable? A. Multiply the sales tax rate (i.e. 6.2 % tax rate by the 65 % construction portion) (.062 x .65 = .0403). Use the 4.03 % as the tax rate. When you multiply your gross sales amount by the adjusted tax rate you will get the correct amount of tax Refresh this page (hit your F5 key) for a More Tech Tips!