Formulas and sources
Each formula this calculator uses, where it comes from, and what it leaves out. "How it works" shows the same formula with your own numbers.
Price including VAT
Add VAT mode
- Total
- the price including VAT
- Amount
- the price before VAT
- VAT rate
- the VAT rate, in percent
The VAT, Amount × VAT rate ÷ 100, is rounded to the nearest cent before it is added, so the total is the amount plus the VAT shown.
Source: Uses the method in HMRC's VAT Notice 700, paragraphs 7.2 and 7.3.1: the VAT is the rate's percentage of the price before VAT [1].
Price before VAT
Remove VAT mode
- Net amount
- the price before VAT
- Total
- the price including VAT
- VAT rate
- the VAT rate, in percent
The VAT in the total is Total × VAT rate ÷ (100 + VAT rate), HMRC's "VAT fraction": one-sixth at 20%. It is rounded to the nearest cent, and the net amount is the total minus it.
Source: Based on HMRC's VAT fraction (VAT Notice 700, paragraph 7.3.1) [1], rearranged to give the price before VAT.
Invoice lines
Invoice mode
- Line gross
- the line's price including VAT
- Line net
- the line's price before VAT
- Line VAT rate
- the line's rate; 0 for Zero Rated and Exempt lines
Each line's VAT is rounded to the nearest cent. The invoice totals are the sums of the rounded lines, also shown for each rate, with exempt lines in their own row.
Source: Uses the method in HMRC's VAT Notice 700, paragraph 7.3.1, for each line [1]. Zero-rated and exempt lines carry no VAT (paragraphs 3.5 and 3.6), and HMRC asks for a separate total of their values (16.5) [1]. An EU invoice names the exemption and, under the reverse charge, says "Reverse charge" (Directive Article 226(11) and (11a) [6]).
Rounding to the cent
Every mode
Half up: a VAT of 0.045 becomes 0.05, so 0.18 at 25% gives 0.05 VAT and a total of 0.23.
Source: CalcTrail's own rule; no publisher. HMRC's VAT Notice 700 (17.5 and 17.6) allows rounding each VAT calculation up or down, which this does [1].
Preset rates
Add VAT and Remove VAT modes
A preset is the country's standard rate. China's 13% is its rate for goods, and Canada's 5% is the federal GST; the provinces that charge HST charge 13% to 15%.
Source: EU rates: the European Commission's Taxes in Europe Database [2] and the EU's Your Europe table [3]. Other countries: each government's own page, linked under the inputs and checked on October 5, 2026. Canada's HST: the Canada Revenue Agency [4]. China: Article 10 of its VAT Law [5].
Sources
- HM Revenue & Customs. VAT guide (VAT Notice 700), paragraphs 3.5, 3.6, 7.2, 7.3.1, 16.5, 17.5 and 17.6. Last updated June 25, 2026.
- European Commission. Taxes in Europe Database (TEDB): VAT rates, standard rates of the 27 member states. Situation on October 5, 2026.
- European Union, Your Europe. VAT rules and rates, List of VAT rates applied in EU member countries. Last checked July 13, 2026.
- Canada Revenue Agency. GST/HST calculator (and rates), table of GST/HST and PST rates by province. Date modified April 1, 2025.
- Standing Committee of the National People's Congress. Value-Added Tax Law of the People's Republic of China (Chinese text), Article 10. Adopted December 25, 2024; in force January 1, 2026.
- Council of the European Union. Council Directive 2006/112/EC on the common system of value added tax, Articles 6(1), 97, 98, 226(11) and 226(11a). Consolidated text of January 1, 2025.
What this calculator does not cover
- It applies the rate you enter to the amount you enter, line by line. It does not decide which rate applies to an item, or whether a sale is zero-rated or exempt.
- It does not handle the reverse charge on business sales between EU countries, the place-of-supply rules, import VAT, margin schemes, or how much input VAT a business can reclaim.
- Presets are standard national rates. Regional rates, such as the Canary Islands' (outside the EU VAT area), are not presets.
Sources checked on .