How to Remove Sales Tax From a Total
Removing sales tax from a tax-inclusive total means working backwards from the total to the pre-tax price. The common instinct — subtracting the tax rate from the total — is wrong. This guide shows the correct reverse formula and why subtraction fails.
Last reviewed: 2026-08-19
Why subtraction does not work
When tax is added to a price, it is calculated on the pre-tax price, not on the final total. So the total is the pre-tax price multiplied by (1 + rate), and you cannot recover the pre-tax price by subtracting the rate from the total.
- Wrong: Pre-Tax Price = Total × (1 − Tax Rate)
- $108 × (1 − 0.08) = $99.36 ← incorrect
Subtracting 8% from a $108 total gives $99.36, but the true pre-tax price is $100. The error is small at low rates and large at high rates: subtracting 20% from a $120 total gives $96 instead of the correct $100.
The correct reverse formula
- Pre-Tax Price = Tax-Inclusive Total ÷ (1 + Tax Rate)
- Tax Amount = Tax-Inclusive Total − Pre-Tax Price
Because the total equals the pre-tax price times (1 + rate), dividing the total by (1 + rate) reverses the multiplication exactly. The tax amount is then whatever is left when you subtract the pre-tax price from the total.
Worked example
A receipt shows a total of $108 and the sales tax rate was 8%.
- Pre-Tax Price = $108 ÷ (1 + 0.08) = $108 ÷ 1.08 = $100
- Tax Amount = $108 − $100 = $8
At a higher rate the method is the same. A $240 total at 20% gives a pre-tax price of $240 ÷ 1.20 = $200 and a tax amount of $40. The division, not subtraction, is what makes the recovery exact.
Removing tax with a calculator
The Sales Tax Calculator has a remove-tax mode that performs this reverse calculation for any rate you enter, so you do not have to handle the division by hand. For the forward direction — adding tax to a pre-tax price — see how to calculate sales tax.
Common mistakes
- Subtracting instead of dividing. The total is (1 + rate) times the pre-tax price, so you must divide by (1 + rate), not subtract the rate.
- Forgetting to convert the percentage. Use 1.08 for 8%, not 108 or 1.8. The decimal conversion (rate ÷ 100) applies just as it does when adding tax.
- Assuming the total includes tax. If a price is pre-tax, removing tax from it produces a meaningless number. Confirm whether the figure is tax-inclusive first.
- Reporting the tax as the pre-tax price. The pre-tax price and the tax amount are different; the tax is the total minus the pre-tax price, never the pre-tax price itself.
The same reverse method works for value-added tax — see the VAT Calculator — and the underlying percentage logic is covered in the Percentage Calculator.