I created it with a custom theme. I created a tax code with the label VAT 12%, but the percentage still uses the 11%, so the VAT will still have the same result with the “Sales Price x 11/12 x VAT 12%” formula.
You can create it like this in the custom theme.,custom field, or footer. You can see the example from this post by @Mabaega "Adding Retention Field and Balance in Invoice Footer" - #7 by Mabaega