What Is Reverse Tax Calculation?
A reverse tax calculation determines the original pre-tax price from a total amount that already includes sales tax. This is useful when you know the total paid but need to separate the product price from the tax amount.
Pre-Tax Price = Total ÷ (1 + Tax Rate)
Tax Amount = Total - Pre-Tax Price
Example: $107 total with 7% tax:
Pre-tax = $107 ÷ 1.07 = $100
Tax = $107 - $100 = $7
When to Use Reverse Tax
- Reconciling receipts and expense reports
- Calculating tax on inclusive-price items
- International purchases (VAT-inclusive prices)
- Splitting costs between tax-exempt and taxable portions
- Accounting and bookkeeping
Forward vs Reverse Tax
Forward: $100 item + 7% tax = $107 total. Simple multiplication.
Reverse: $107 total with 7% tax = $100 pre-tax. Requires division, not subtraction. A common mistake is subtracting 7% of $107 ($7.49), which gives $99.51 — incorrect!
How to Use
Enter the total amount paid and the tax rate percentage. The calculator shows the pre-tax price and tax amount instantly.
VAT and International Taxes
Many countries use Value Added Tax (VAT) where prices include tax. The reverse tax formula is essential for extracting the base price from VAT-inclusive amounts.
US State Sales Tax Rates
US sales tax varies by state from 0% (Delaware, Oregon, Montana, New Hampshire) to over 9% in some jurisdictions when combining state and local rates.