UK VAT Add, Remove and Flat-Rate Calculator
Add or remove VAT, inspect net and gross amounts, and compare an optional flat-rate percentage.
Answer-first introduction
Adding or removing VAT from a price is different from estimating an amount under the Flat Rate Scheme. Check the selected calculation mode and the rate that applies to your circumstances before using the result.
What this calculator explains
Adding VAT and removing VAT use different formulas. To add 20%, multiply the net amount by 1.20. To remove 20% from a VAT-inclusive amount, divide by 1.20; subtracting 20% from the gross amount gives the wrong answer.
Flat Rate Scheme mode remains separate from ordinary invoice VAT. It applies the selected sector percentage to VAT-inclusive turnover and explains that eligibility, limited-cost-trader rules and special adjustments may change the amount due.
How the estimate is calculated
- For add mode, multiply the net amount by 1 plus the selected VAT rate.
- For remove mode, divide the gross amount by 1 plus the selected VAT rate.
- Calculate VAT as gross minus net.
- For invoice mode, calculate each line using the correct selected treatment and sum rounded outputs according to the implementation rule.
- For Flat Rate Scheme mode, multiply VAT-inclusive turnover by the selected official percentage.
- Display limited-cost-trader, capital-asset and eligibility warnings where relevant.
Formula
Add VAT: gross = net × (1 + rate); remove VAT: net = gross ÷ (1 + rate); VAT = gross − net
Worked example
At the standard 20% rate, a net amount of £1,000 has £200 VAT and a gross total of £1,200. To remove VAT from £1,200, divide by 1.20 to get £1,000 net, then subtract to find £200 VAT. For a Flat Rate Scheme example, VAT-inclusive turnover of £120,000 at an entered 12.5% sector rate produces an illustrative payment of £15,000 before any eligible discount or special adjustment.
Rules and assumptions
- The main VAT rates remain 20% standard, 5% reduced and 0% zero rate, subject to the legal classification of the supply.
- To remove 20% VAT from a gross amount, divide by 1.20; subtracting 20% from the gross amount is incorrect.
- Flat Rate Scheme mode must use the selected business-sector percentage and remain separate from ordinary invoice VAT.
Included in the estimate
- Add and remove VAT
- 20%, 5% and 0% rate modes
- Net, VAT and gross breakdown
- Multiple invoice lines
- Flat Rate Scheme percentage model
- CSV or invoice-summary export
Not included or not guaranteed
- A decision about exempt, outside-scope or zero-rated treatment
- VAT registration or deregistration advice
- Partial exemption and international VAT
- A complete VAT return
- Automatic Flat Rate Scheme eligibility
How do I add 20% VAT?
Multiply the net amount by 1.20. The difference between gross and net is the VAT amount.
How do I remove 20% VAT?
Divide the VAT-inclusive amount by 1.20. Do not simply subtract 20% from the gross amount.
What are the main UK VAT rates?
The standard rate is 20%, the reduced rate is 5% and zero-rated supplies use 0%, but classification depends on the supply.
What is VAT-exempt?
Exempt supplies are not the same as zero-rated supplies. The calculator does not classify the transaction; the user selects the treatment based on official guidance.
How does the Flat Rate Scheme work?
An eligible business uses a sector percentage on VAT-inclusive turnover and normally cannot reclaim most input VAT, with limited exceptions.
Can I use the calculator for an invoice?
Yes for arithmetic, but invoice-date, tax-point, rounding and record requirements still need to be followed.
Official sources
Applicable period: 2026-04-06/2027-04-05 · Last reviewed: September 3, 2026
Related tools
Save the calculation with the invoice
Export net, VAT, gross, selected rate and calculation mode so the arithmetic can be reviewed later.