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Add a custom tax rate to a line

Most of the time you apply one of your organisation's saved tax rates to an invoice line — for example Standard (20%). But when a line needs a rate that isn't in your list, you can…

Add a custom tax rate to a line

Most of the time you apply one of your organisation's saved tax rates to an invoice line — for example Standard (20%). But when a line needs a rate that isn't in your list, you can enter a custom tax rate (or a fixed tax amount) on that line, right in the line editor. It applies to that one line only.

This works both when creating a sales invoice and when editing a draft, through the Add Line Item editor.

Before you begin

  • The invoice must be a Draft. You can change a line's tax while the invoice is a draft; once it is issued the lines are fixed.
  • Open the draft (or start a new invoice) so the Line Items card is visible.

Steps

  1. In the Line Items card, select Add Line Item to open the line editor. (To change a line you already added, select its edit (pencil) button — the editor re-opens with the line's details.)
  2. Fill in the line as usual — Product (optional), Description, Quantity, Unit Price, and any line Discount %.
  3. In the Tax Configuration card, at Tax Type, choose how tax is worked out for this line:
    • System Tax Rate (the default) — pick one of your saved rates from the Tax Rate list (for example Standard (20%)), or choose -- No tax --.
    • Custom Rate % — type your own percentage in Custom Tax Rate % (for example 7.5). You can add an optional Tax Description to label it, such as "Special VAT".
    • Custom Amount — type a fixed tax figure in Custom Tax Amount (for example 15.00, in the invoice's currency), with an optional Tax Description such as "Import duty".
  4. Select Add line (or Add & add another to keep adding). When you are editing a line you already added, the button reads Save line.
  5. Select Save Draft.

The line then shows its tax as, for example, "7.5% (custom)" or "Fixed: £15.00", with your description beneath it, and the invoice's Total Tax, Total and Amount Due update straight away.

How the tax is worked out

  • A Custom Rate % is applied to the line's net amount after any line discount — exactly like a saved rate. So 7.5% on a £100 line (after discount) adds £7.50 of tax.
  • A Custom Amount is used exactly as you typed it, whatever the line's value.
  • A custom percentage is limited to 0–100%.

Good to know

  • A custom rate or amount lives on that line only. It is not added to your saved tax rates and can't be reused elsewhere — you enter it again on the next line that needs it. To have a rate available for reuse, it needs to be in your saved tax rates.
  • Custom tax still contributes to the invoice's VAT totals and your VAT Summary report in the normal way.
  • Custom tax works the same way whether you are creating a new invoice or editing an existing one, and whether or not the line has a product — the rate or amount you enter is always the one used.
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