Sales Tax & Reverse VAT Calculator
Calculate sales tax additions or reverse-engineer net base and tax amounts from total receipts.
How Reverse Tax Works
To extract sales tax from a gross receipt, you don't simply multiply the total by the tax rate. Instead, divide the gross amount by 1 + (Rate / 100). For a 10% rate on $110: $110 ÷ 1.10 = $100 net base.
Expense Claims & Auditing
Essential for freelancers and small businesses preparing quarterly BAS, GST, or VAT returns where vendor invoices display only the gross card total.
Frequently Asked Questions
How do I add sales tax to a price?▼
Multiply the price by 1 plus the rate. A $100 item with 10% tax costs $100 × 1.10 = $110. Use Add Tax mode and enter the pre-tax amount.
How do I take GST or VAT out of a total?▼
Divide the total by 1 plus the rate. A $110 receipt with 10% GST contains $110 ÷ 1.10 = $100 before tax, so $10 is tax. Use Extract Tax mode.
Why not just multiply the total by the tax rate?▼
Because the tax is a percentage of the pre-tax price, not of the total. Taking 10% of $110 gives $11, which is wrong; the real tax is $10.
Which tax rates can I enter?▼
Any rate from 0% to 100%. The presets cover common standard rates, and you can type your own, such as 8.25%.
Is this tax advice?▼
No. It is an arithmetic tool. Check your local rules for rounding, exempt items and which rate applies.
Is my data sent to a server?▼
No. The calculator runs entirely in your browser, so nothing you enter is uploaded, stored or tracked. Once the page has loaded it keeps working without a connection.