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Reverse Sales Tax Calculator

Find the pre-tax price from a gross amount.

How it is calculated

When a price already includes sales tax or VAT, the pre-tax amount is net = gross / (1 + rate/100) and the tax is tax = gross − net. Enter the tax-inclusive price (gross) and the tax rate as a percentage. Dividing is the key step: you cannot simply subtract the rate percentage from the gross, because the tax was added on top of the net, not on top of the gross. The tool accepts a rate of 0 and any non-negative amounts. It applies the single rate you enter; it does not know which rates apply in your country or to your product, and mixed-rate baskets need to be split by hand. Results are shown in dollars to the cent.

Worked example

A receipt shows a total of 120 including a 20% tax. The divisor is 1 + 20/100 = 1.20. Net price: 120 / 1.20 = $100.00. Tax portion: 120 − 100 = $20.00. Note that subtracting 20% of 120 would give 96, which is wrong.

Try this example →

Common mistakes

  • Subtracting the rate percentage from the gross (120 × 0.80 = 96) instead of dividing by 1.20.
  • Entering a price that does not include tax as the gross figure.
  • Using the wrong rate, for example a reduced rate for an item that carries the standard rate.
  • Applying one rate to a bill that mixes taxed and exempt items.
  • Entering the rate as a decimal (0.2) rather than as a percentage (20).

About this calculator

Given a tax-inclusive (gross) price and the tax rate, this calculator works backward using net = gross / (1 + taxRate) to split the amount into the pre-tax price and the tax portion — the opposite direction from a normal sales tax calculation, which adds tax onto a known net price.

Retailers and accountants use it to recover the net revenue and tax collected from a receipt total, freelancers use it to figure out how much of an invoice total is actual income versus VAT/GST owed to the government, and shoppers use it to see how much tax they actually paid on a purchase. The calculator handles any tax rate you enter, so it works for VAT, GST, or standard US-style sales tax alike.

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