Value Added Tax is part of almost every business transaction in the UK, yet the arithmetic behind it catches people out constantly. Whether you are pricing a product, checking a supplier invoice or preparing a VAT return, you need to move confidently between net and gross amounts. Here is a clear, step-by-step method that works for any VAT rate.
A quick reminder of the UK VAT rates
The UK currently has three rates:
- Standard rate: 20% – most goods and services
- Reduced rate: 5% – for example domestic energy and some renovation work
- Zero rate: 0% – for example most food, children's clothes and books
The formulas in this guide work for any rate; just swap in the right percentage.
Step 1: Adding VAT (net to gross)
When you have a price excluding VAT and need the total the customer will pay:
- Take the net price.
- Multiply it by the VAT rate as a decimal (20% becomes 0.20) to find the VAT amount.
- Add the VAT amount to the net price.
Or use the shortcut: net × 1.20 = gross (at the 20% rate).
Example: A designer quotes £800 before VAT.
- VAT = £800 × 0.20 = £160
- Gross total = £800 + £160 = £960
Step 2: Removing VAT (gross to net)
This is where most mistakes happen. You cannot simply take 20% off the gross amount – that understates the net figure. Instead:
- Take the gross price (VAT included).
- Divide it by 1.20 (at the 20% rate) to find the net amount.
- Subtract the net amount from the gross to find the VAT element.
Example: An invoice totals £960 including VAT.
- Net = £960 ÷ 1.20 = £800
- VAT element = £960 − £800 = £160
Note the trap: 20% of £960 is £192, which is wrong. The VAT fraction of a VAT-inclusive price at the standard rate is one-sixth (about 16.67%), not 20%.
Quick-reference multipliers
| You have | You want | Formula (20% rate) |
|---|---|---|
| Net price | Gross price | × 1.20 |
| Gross price | Net price | ÷ 1.20 |
| Net price | VAT amount only | × 0.20 |
| Gross price | VAT amount only | × 1/6 (≈ 0.1667) |
Keep this table somewhere handy – it covers nearly every VAT calculation you will meet day to day.
The 5% reduced-rate version
The same logic applies with a different multiplier:
- Adding: net × 1.05 = gross
- Removing: gross ÷ 1.05 = net
Example: A domestic gas bill of £200 before VAT at 5% comes to £200 × 1.05 = £210 gross.
When do you add VAT, and when do you remove it?
- Adding is for quoting and invoicing: your list prices are usually net, and the customer pays gross.
- Removing is for checking and reclaiming: supplier invoices show gross totals, and you need the net cost and the VAT element for your books and your VAT return.
If you ever receive a quote and are unsure whether it includes VAT, ask. Assuming wrongly is one of the most common causes of margin surprises for small businesses.
Rounding
HMRC allows VAT to be rounded to the nearest penny. You may round each line of an invoice or the invoice total, and both approaches appear in real accounting software. Whichever method you use, be consistent, and make sure the VAT shown on your invoices agrees with what you report on your VAT return.
Three common mistakes to avoid
- Taking 20% off a gross price to find the net – divide by 1.2 instead.
- Charging VAT when you are not registered – only VAT-registered businesses may add VAT to their invoices.
- Applying 20% to everything – check whether the goods or services are reduced-rated, zero-rated or exempt before you calculate.
Putting it into practice
Work through a few real invoices with the steps above until dividing by 1.2 feels automatic. If you would like a longer set of worked examples – including mixed-rate baskets and awkward rounding cases – this guide to calculating VAT step by step covers each scenario in detail.
Once these two formulas are second nature, VAT stops being a source of invoice errors and becomes simple arithmetic.
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