ITrack/Pro/Sales Tax

How to calculate

For every lineitem that has the "tax" checkbox checked, the quantity is multiplied by the sum of the core price and the regular price: quantity * (core + price).

This number from every lineitem is added together into the subtotal.

The subtotal is multiplied by the tax percent (which is determined by the Tax Item setting above the lineitems).

This number is added to the subtotal to get the total.

It's important to remember that sales tax is calculated against the sum of all taxable lineitems, and not on the lineitems individually.