🧾 Sales Tax Reverse Price Calculator
If you know the final tax-included price and the sales tax rate, this calculates what the pre-tax price and tax amount must have been.
Why you divide instead of subtracting
Tax was added to a smaller number than the one you are holding, so the total has to be divided back down:
pre-tax price = total / (1 + rate/100)
tax amount = total - pre-tax price$107.00 at 7% divides to exactly $100.00 pre-tax with $7.00 of tax. Take 7% off the total instead and you get $99.51 - wrong by 49c, because that 7% was charged on the $100, not on the $107. The error grows with the rate: at 20% the shortcut is out by 4% of the price.
Getting the rate and the reading right
- Use the combined rate you actually charged, not the headline state one. In much of the US the state rate is topped up by county, city and special-district add-ons, and the receipt shows the sum.
- Expect the odd cent. The till worked forwards, rounding tax to the nearest cent, so working backwards can land a cent away from the original price. For bookkeeping, use the tax figure printed on the receipt.
- One rate per total. A basket mixing goods taxed at different rates, or taxed and exempt items together, cannot be unpicked from a single number - split the receipt by line and reverse each group.
- A 0% rate returns the total unchanged, which is correct, not an error.
Frequently asked questions
How do I find the price before sales tax?
Divide the tax-included total by 1 plus the rate as a decimal. At 7%, divide by 1.07: a $53.50 total is $50.00 before tax and $3.50 of tax.
Can I just take the tax percentage off the total?
No, and it is not close enough at higher rates. Subtracting 7% from $107 gives $99.51 rather than $100, understating the pre-tax price and the tax with it.
Does the same method work for VAT or GST?
Yes. Any tax added as a percentage on top reverses the same way. A VAT-inclusive 120 at 20% divides by 1.2 to give 100 net and 20 of VAT.