VAT Calculator UK — Add VAT or Remove It From a Total

Add VAT to a net price or use the reverse VAT calculator to extract VAT from a gross amount — at any rate (5%, 15%, 18%, 20%, 25%, or custom). This free VAT calculator online shows the full breakdown instantly: pre-VAT price, VAT amount, post-VAT total, and a visual VAT burden gauge.

Created by Ashar PervaizLast updated 24 October 2026

Two Directions, and Only One of Them Is Obvious

Every VAT calculation goes one of two ways. You either have a price without VAT and need the total, or you have a total that already includes VAT and need to work backwards. The first is a multiplication most people get right. The second is where nearly all VAT errors happen, because the instinctive move — subtract the percentage — is wrong.

Take a gross figure of 120 at a 20% rate. Subtracting 20% gives 96. The correct answer is 100. The gap is not a rounding artefact; it is a structural error that recurs on every invoice processed that way.

The reason is what the percentage is applied to. VAT is 20% of the net price, not 20% of the gross. When you subtract 20% from the gross you are taking a fifth of the wrong number — a fifth of 120 rather than a fifth of 100. Getting this one distinction right removes the majority of VAT mistakes.

Adding VAT to a Price

Going upward is straightforward. Convert the rate into a multiplier and multiply once:

Gross = Net × (1 + rate)

Calculating the VAT separately and then adding it gives the same answer, but the single multiplication is worth the habit — it removes an intermediate rounding step, which matters once you are adding up a column of invoice lines.

Removing VAT: the Reverse Calculation

Going downward is a division by the same multiplier, never a subtraction:

Net = Gross ÷ (1 + rate)

A gross price of 600 at 20% is 600 ÷ 1.20 = 500.

Notice that the error grows with the rate. At 5% the shortcut is out by under two units and might survive unnoticed; at 25% it is out by thirty. Anyone reconciling accounts in a high-rate jurisdiction finds this quickly. Anyone in a low-rate one may not, which is the more dangerous position.

Pulling Out Just the VAT Element

Often you do not want the net figure at all — you want to know how much of a gross amount is tax, to record it or reclaim it. Two routes give the same answer.

VAT = Gross − (Gross ÷ (1 + rate))
or, in one step: VAT = Gross × rate ÷ (100 + rate)

The second form produces a set of fractions worth committing to memory, because they turn the calculation into arithmetic you can do without a calculator at all.

A receipt for 120 at a 20% rate contains 20 of VAT, because 120 ÷ 6 = 20. That single fact makes it possible to sanity-check almost any gross figure in your head, which is the fastest way to catch an invoice that has been calculated the wrong way round.

Where a Penny Goes Missing

Two people can calculate the same invoice correctly and disagree by a small amount, and the reason is rounding order rather than arithmetic.

Consider three lines at 12.49 each, VAT at 20%. Rounding the VAT on each line gives 2.50 three times, totalling 7.50. Calculating VAT on the summed net of 37.47 gives 7.494, which rounds to 7.49. Both methods are defensible and they differ by a penny.

The practical rule is to pick one convention and apply it consistently, since the discrepancy compounds across a ledger rather than cancelling out. Where a tax authority specifies which method to use on invoices, that instruction overrides preference. Keeping unrounded values through intermediate steps and rounding only at the final total is the approach that produces the fewest reconciliation problems.

Which Rate Applies, and the Zero-Rated Trap

Most systems run more than one rate. A standard rate covers most goods and services, a reduced rate applies to specified categories, and some items carry no VAT at all. The distinction that catches businesses out is between two things that both show 0 on an invoice and are not the same.

Zero-rated and exempt look identical on a customer receipt and behave in opposite ways behind it. A business making zero-rated supplies charges nothing but still recovers the VAT it paid on its own costs, often ending each period in a refund position. A business making exempt supplies recovers nothing, so the VAT on its purchases becomes a real cost absorbed into its margins. Which category a product falls into is set by law and is not a choice.

What Registered Businesses Actually Pay

For a VAT-registered business, VAT is not a cost — it is a flow passing through. What gets paid over is the difference between two totals:

Payable = Output VAT (charged on sales) − Input VAT (paid on purchases)

A business charging 12,000 of output VAT in a quarter while paying 8,000 of input VAT remits 4,000. If the figures reverse — common for a business in a period of heavy investment, or one making zero-rated supplies — the result is a reclaim rather than a payment.

This is why the direction of a calculation matters so much in bookkeeping. Recording a gross amount where a net one belongs, or the reverse, does not just misstate one line; it misstates the reclaim position for the whole period. It is also why the reverse calculation gets used far more often than people expect — supplier receipts usually show a gross total, and the input VAT has to be extracted from it before anything can be reclaimed.

Rates and category rules differ by country and change over time, so confirm the current rate with your own tax authority before filing anything. For the background on how VAT works as a system, see our guide to what VAT is and how it is charged. For working out what you owe on income rather than sales, the income tax calculator and the freelancer tax calculator handle those separately. Both directions of the sum — adding VAT to a net price and stripping it back out of a gross one — are set out in our library of formulas, which is the quickest way to see why removing VAT is not the same as subtracting the rate.

Adding VAT and stripping it out are the two sums people mix up, and the wording usually gives away which one is wanted. The AI calculator answers "add VAT to 150" and "remove VAT from 180" as typed, which is a quick way to check you have asked for the one you think you have.

VAT is the step after pricing, not part of it — you set a price from cost and margin first, then add the tax to what you arrived at. The markup calculator does that first half, including the difference between a markup and a margin that catches most people out.

VAT Questions, Answered