My invoice has lines at different VAT rates and some at zero; how do I calculate it with the calculator?

Why not enter the invoice total once?

Because the VAT calculator applies one rate to the whole amount; that is stated in its assumptions. Enter the full 650 at 15 and it would tax the zero-tax lines too, showing 97.5 of tax instead of 60, so the customer would be overcharged by 37.5.

The idea is to treat a mixed invoice as several small invoices, each with a single rate, and then add them together at the end.

Step by step

1. Sort the invoice lines into groups: every line with the same rate goes in one group.
2. Add up each group before tax. In this example, a taxable group of 400 and a zero-tax group of 250.
3. In add mode, enter 400 with its rate of 15: tax 60, gross 460.
4. Enter 250 with a rate of 0: the tool notes the rate is zero and there is no tax, so the gross stays 250.
5. Add them up: 650 net, 60 tax, 710 gross.

Showing it on the invoice

Your customer and your accountant both want to see where the tax came from. So rather than one tax line, give a short summary per rate:

• Lines at 15: amount 400, tax 60.
• Zero-tax lines: amount 250, tax 0.
• Total due: 710.

A caution if you use the Basic invoice generator: it has a single rate field applied to the whole invoice, so it does not fit a mixed invoice as it stands. Either issue one invoice per rate or use a system that supports several rates. The template is basic and is not a certified e-invoicing system.

The question the calculator cannot answer

Which lines are exempt, which are zero-rated and which take the standard rate? That is not arithmetic. The difference between exempt and zero-rated affects how things are recorded and reported, even though both show zero tax on the invoice. Your tax authority sets it and your accountant can explain it; the calculator only works with what you enter.