HaatBeatHow it's calculated
The entered percentage is divided by 100 before using it in the formula. The tax is rounded once to the currency’s minor unit, then the other displayed amount is found by subtraction so the parts add up.
Assumptions
- The 18% starting value is an illustrative input. Enter or confirm a custom rate before a result appears; no rate is inferred from your region.
- This is a single-item estimate with one rate. Exemptions, input credits, compound taxes, shipping and invoice rules are outside this calculation.
- Amounts must use the selected currency’s minor unit. Tax uses decimal half-up rounding; local invoice rules may differ.
Worked example
At an illustrative 18% custom rate, adding tax to 1,000 gives 180 tax and 1,180 total. Removing tax from 1,180 gives a 1,000 base and 180 tax.
Questions
Why does removing 18% not mean subtracting 18% of the total?
The entered total already contains tax. Divide it by 1.18 to find the base, then subtract the base from the total to find tax.
Does the page know my local rate?
No. The rate shown at first is only an example. Enter or confirm the rate that applies to your calculation.
Can I use a 0% rate?
Yes. The tax is zero and the price before and after tax is the same.
Why might my invoice differ?
Local rules can use different rounding, exemptions, multiple rates or line-item treatment. This page shows one item at one entered rate.