So, if your subtotal is $1,000 and you need to apply sales tax at 5 percent, multiply $1,000 by 0.05 to arrive at $50. Add your subtotal to the tax your're charging to arrive at the total amount due.

Example of a Pro Forma Invoice. Pro forma invoices display a price quote for a prospective sale, import or export of goods. These invoices are often used during negotiations to list the terms of ...