Calculation Subtotal Merge Tag This form uses the Calculation Subtotal Merge Tag snippet to add 10% tax. Purple Antlers Price: Mounting Options Wooden Mount Granite Mount Golden Mount Tax Price: $0.00 This is where the magic happens. This is a Calculation Product field. The formula uses the {subtotal} merge tag to more readily calculate the 10% tax: {subtotal} * 0.1Shipping Total This demo is powered by Gravity Forms v2.5.16.