--- title: "UK Discount Calculator: Stacked Offers and VAT | AumnI tools" description: "Stack percentage and pound-off vouchers in order, see the real saving, and split the VAT out of a shelf price at 20%, 5% or 0% with the rate menu." url: https://aumnitools.com/uk/tool/discount-calculator category: "Lifestyle" country: "United Kingdom" updated: 2026-11-08 --- # Discount Calculator A British shelf price already contains VAT, so the number you pay after a voucher is not the number the tax is charged on. This calculator takes each offer from the running price, shows the true saving, and works out the VAT inside the final price at the standard, reduced or zero rate. ## United Kingdom rules and figures - UK VAT comes in three rates: 20% standard, 5% reduced and 0% zero. - Shelf prices in UK shops include VAT, so the amount on the label is the amount you pay. - At the 20% rate the VAT inside a price is one sixth of it, so a £60.00 price holds £10.00 of VAT. - The rate menu in this tool starts on the 20% standard rate and lets you switch to 5% or 0%. Sources: [GOV.UK: VAT rates](https://www.gov.uk/vat-rates) (checked 2026-11-08) ## How the discount calculator works Offers are applied one after another, each from what the last one left, either as a percentage or as a fixed pounds amount. The VAT switch then separates the net price and the tax from the final price, because UK prices include VAT. Formula: `net = final ÷ (1 + VAT rate); VAT = final − net; at 20%, VAT = final × 20 ÷ 120` - The tax menu lists Standard rate 20%, Reduced rate 5% and Zero rate 0%, with Standard selected. - Price includes VAT is on from the start, which matches how prices appear in UK shops. - The opening price is 120 in pounds with a 30% Sale and a 20% Extra code, so the first screen shows a 44% saving, not 50%. - A fixed pounds offer is capped at the price left, so it can never make the price negative. - Switching the symbol box changes the label only; no exchange rate is applied. ## How to use the discount calculator 1. **Enter the original price.** Type the shelf price, a quantity and a currency symbol of up to three characters. 2. **Add discounts in order.** Each row has a label, a value and a switch between percent and a fixed amount. The numbers show the order they are applied in. 3. **Set the tax treatment.** Enter a rate and say whether the price already includes it. The tax card shows the net price, the tax and the amount payable. Where a country has several rates, a menu above the field lists them. 4. **Work backwards from a sale price.** Enter what you paid and the advertised percentage to see the original price that figure implies. 5. **Compare multi-buys and pack sizes.** Use the deals tab with the price of one item, then the unit-price tab to compare packs on cost per unit. ## Example: £80.00 with 25% off, then £10.00 off A quarter off £80.00 leaves £60.00, and the £10.00 voucher then leaves £50.00, saving 37.5% overall. With VAT at 20% included, the net price is £41.67 and the VAT is £8.33. At the 5% reduced rate the same £50.00 would hold £2.38 of VAT. Taking the £10.00 first and the 25% second gives £52.50. ## When to use the discount calculator - **Checking a sale plus a voucher code.** Enter the sale percentage first and the code second to see the final price and the combined saving. - **Finding the VAT in a receipt price.** Leave Price includes VAT on and read the net price and VAT lines. - **Comparing a pound-off coupon with a percentage.** Add both in each order and see which leaves the lower price. - **Testing an advertised saving.** Use Work backwards with what you paid and the claimed percentage. ## What the discount calculator does not do - One VAT rate applies to the whole price, so a basket mixing 20% and 5% items needs separate runs. - Quantity multiplies a per-item result, so a basket-wide voucher belongs against a quantity of 1. - Figures are unrounded inside the maths and shown to two decimals, so pennies can differ from a till. - There are no exchange rates, so the symbol box only changes the label. - Work backwards accepts a single percentage, not a stack. ## When something else is a better fit - **When you want to turn one percentage into another**, use the [Percentage Calculator](https://aumnitools.com/tool/percentage-calculator.md). - **When you are calculating income tax rather than VAT**, use the [Tax Calculator](https://aumnitools.com/tool/tax-calculator.md). - **When you are checking the rules on VAT rates**, use the GOV.UK VAT rates page. ## Questions about the discount calculator ### Why is 25% off then £10 off not 35 pounds off? Because the percentage comes first. 25% of £80.00 is £20.00, leaving £60.00, and the £10 then takes it to £50.00, a saving of £30.00. ### Does the order of offers matter? Yes when you mix a percentage and a fixed amount. Taking £10 first and then 25% leaves £52.50 against £50.00 the other way. ### How much VAT is inside a UK price? At the 20% standard rate it is one sixth. In £50.00 that is £8.33, with £41.67 as the net price. ### What does the reduced rate change? It moves the split only. The shelf price stays £50.00, but the VAT inside falls to £2.38 at 5%. ### How do I check a claimed sale price? Use Work backwards. Paying £60.00 after an advertised 25% means the original was £80.00. ## Related tools - [Percentage Calculator](https://aumnitools.com/tool/percentage-calculator.md): Eight percentage questions solved from two numbers, with each step shown - [Tax Calculator](https://aumnitools.com/tool/tax-calculator.md): Estimates US federal income tax, FICA and state tax for 2026 by filing status - [Tip Calculator](https://aumnitools.com/tool/tip-calculator.md): Works out a tip and total from a bill, with tax handling, rounding and bill splitting ## About this page Runs in your browser: what you enter is processed on this device and is not uploaded. Last checked against the tool's code on 2026-11-08. Interactive version: https://aumnitools.com/uk/tool/discount-calculator