I’m trying to modify the Editable invoice from CSS-Tricks. I need to add a column below "subtotal" for Taxes, which is a percentage value. So basically, I need the subtotal to be the amount of the line items, then taxes to be a set percentage of the sub-total, and have both numbers add up to the total.
Probably not what you want to hear, but the answer is to download the example and start playing with it. Change stuff, figure out what is going on. Then add to it. If stuff breaks, try and figure out why. Eventually you’ll get to what you need =)