How do I make a tailoring invoice total the amount agreed with the customer?

A tailor often agrees a round price with the customer: "the two garments with the fabric for 160". Working out by hand the discount that lands the total on that figure, tax included, is tedious, and the Target amount field does it for you.

Steps

1. Enter the invoice lines, services and products, as usual.
2. In Invoice details, type in the yellow Target amount field the total you agreed, tax included.
3. The discount is worked out at once, the total shows your amount, and the initial payment follows it.
4. Save: the total is stored exactly equal to the target amount, with no rounding difference.

Example

A service at 150 and products at 20, tax 5%: the total before discount is 178.500. You type 160 in the target amount; the discount becomes 17.619, the tax 7.619 and the total 160.000.

Notes

• The field never raises the price: an amount above the total before discount means no discount.
• If you then type in the discount field, the discount is what counts.
• If you change a line after typing the target amount, the target is dropped and the discount stays as shown; so type the target amount last.
• If the target amount equals the subtotal before tax, the discount and the tax come out equal. That is right: it means the price includes tax.
• On the printout the invoice tax is spread over the lines after each line's share of the discount, so the lines add up to the invoice tax.