Reverse VAT calculator
Start from the VAT-inclusive total and work backwards to the net and the VAT, divided correctly rather than subtracted wrongly.
Guide
How to use it
- Enter the gross amount, the figure with VAT already inside it.
- Pick the rate the seller charged (20% unless the invoice says otherwise).
- Read the net tile for the pre-VAT price and the VAT tile for the reclaimable slice.
- Sense check: at 20%, the VAT should be exactly one sixth of the gross.
Examples
Worked examples
An invoice totals £1,470 including VAT. 1,470 ÷ 1.2 = £1,225 net, £245 VAT. If the invoice's own lines say otherwise by more than pennies, query it.
A £54 stationery receipt with no VAT breakdown: £45 net, £9 VAT to the reclaim column, exactly one sixth of the total.
Taking 20% off £120 gives £96, which is wrong: the true net is £100. Subtracting the rate from the gross always understates the net.
Method
How it works
Gross = net × (1 + rate ÷ 100), so net = gross ÷ (1 + rate ÷ 100) and the VAT is the difference. At 20% that makes VAT one sixth of the gross (20⁄120), the fraction bookkeepers memorise. The tool divides properly and shows the formula every time.
Arithmetic, not tax advice; rates as published at 8 August 2026. Nothing you enter leaves your browser.
FAQ
Frequently asked questions
How do I work out the VAT inside a total?
Divide the gross by 1.2 to get the net, and the VAT is the difference. £600 gross is £500 net and £100 VAT. For 5%, divide by 1.05.
Why is the VAT not just 20% of the total?
Because the 20% was charged on the net, which is smaller than the gross. VAT is 20⁄120 of the gross, one sixth, not one fifth. Taking 20% of the gross overstates it.
What is the quick fraction for 20% VAT?
VAT is one sixth of the gross. £120 gross ÷ 6 = £20 VAT. At 5%, VAT is 1⁄21 of the gross.
When would I need to reverse VAT?
Checking an invoice's arithmetic, splitting a receipt into net and reclaimable VAT for bookkeeping, working back to a supplier's net price, or budgeting when quotes are given gross.
The invoice shows different figures than this page. Who is wrong?
Possibly neither: invoices often calculate VAT per line and round each line to the penny, so totals can differ from a single calculation by a penny or two. Bigger gaps mean a wrong rate or an arithmetic slip.
Does this work for other countries' VAT?
Yes, type the rate into the custom box: 23% for Ireland, 19% for Germany, 21% for the Netherlands. The maths is identical, only the percentage changes.
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