Check the relationship between net invoice value, VAT and gross total. Work in either direction and enter the VAT rate applicable to each group of invoice lines.
VAT = net × rate / 100. Gross = net × (1 + rate / 100). Net = gross / (1 + rate / 100).
Two net lines of £100 at 20% and £50 at 5% give VAT of £20 + £2.50 = £22.50 and gross total £172.50. Applying 20% to the whole £150 would be wrong.
For invoices with multiple VAT rates, calculate each group separately and add the totals. Discounts, rounding per line, reverse charges and special schemes need their own treatment. This tool checks arithmetic, not the legal validity of an invoice.
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Editorial responsibility: Nicolas Belotti · Methods and testing · Report an error
English edition: 16 September 2026.