📄 Invoicing guide

How to calculate tax on an invoice

Adding tax to an invoice is straightforward once you know whether your prices already include it. This guide explains the two approaches, walks through the maths, and shows how SafeKit does it for you. It is general guidance, not tax advice — which taxes apply to you depends on your local rules.

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Tax-exclusive vs tax-inclusive

Tax-exclusive pricing means your listed prices do not include tax, so tax is added on top of the subtotal. Tax-inclusive pricing means your prices already contain the tax, so the invoice shows how much of the total is tax rather than adding more. Business-to-business invoices are commonly tax-exclusive; consumer prices are often tax-inclusive.

The calculation, step by step

  1. Add up the line totals to get the subtotal.
  2. Apply any invoice-level discount to the subtotal.
  3. Multiply the discounted subtotal by your tax rate to get the tax amount (for exclusive pricing).
  4. Add the tax to the discounted subtotal to get the total due.

A worked example

Subtotal $1,000, a 10% discount (−$100) leaves $900. Sales tax at 8% on $900 is $72. The total due is $972, and the invoice shows $72 as tax. SafeKit runs this calculation automatically as you type, and supports multiple taxes, tax-exempt items, and both inclusive and exclusive pricing.

Frequently asked questions

What is the difference between VAT, GST and sales tax?
They are different names for consumption taxes used in different countries — VAT (much of Europe), GST (e.g. Australia, India, Canada) and sales tax (e.g. the US). The invoice mechanics are similar; the rates, rules and registration thresholds differ by country.
Do I have to charge tax on every invoice?
Only if you are registered to collect it and the item is taxable. Some items and clients are tax-exempt. Check your local rules, and mark exempt items accordingly.

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