Check the "VAT rate" (it’s pre-set to the UK standard rate of 20%)
Enter the amount – net or gross price. Check full VAT rates list below
Click "Remove VAT" or "Add VAT" depending on what you want
If you want to add VAT to the price, you just need to divide the price by 100 and then multiply by (100 + VAT rate). That's all, you got the price including VAT - Gross price.
If you want to subtract VAT from the price, you need to divide the price by (100 + VAT rate) and then multiply by 100. Now you know the price excluding VAT - Net price.