The calculations, step by step
| Step | Formula |
|---|---|
| Line total | quantity × unit price |
| Subtotal | sum of line totals |
| After discount | subtotal − discount |
| Tax | taxable amount × tax rate |
| Grand total | after discount + tax + shipping |
Worked example: 3 items at 20.00 and 2 at 12.50 give lines of 60.00 and 25.00 and a subtotal of 85.00. With a 10% discount (8.50) the taxable amount is 76.50. At 20% tax (15.30) and 5.00 shipping the total is 96.80. If the invoice says 98.30, that is a 1.50 discrepancy the checker would flag.
What you see after a check
Each step above appears as a result with the invoice value, the calculated value and the difference. Passed checks are marked clearly, so you can see what was verified and not just what failed.
Related
For tax formulas see how to calculate VAT on an invoice. For a wider view of what can go wrong see common invoice errors. Upload an invoice to run the checker.