Understanding Reverse Tax Calculation
Sometimes you have a receipt with just the total amount, or you want to know how much tax was included in a "tax-in" price.
The Math Behind It
If you want to remove tax from a total, you can't just multiply the total by the tax rate. You must use the inverse formula.
Formula: Pre-tax Amount = Total Amount / (1 + Tax Rate)
Example: Ontario (13% HST)
If you paid $113.00 for an item:
- Tax Rate = 0.13
- divisor = 1.13
- $113.00 / 1.13 = $100.00
The tax amount is the difference: $113.00 - $100.00 = $13.00.
Using Our Tool
Our Canada GST/HST Calculator has a built-in "Remove Tax" mode that does this math for you instantly across all provinces.
Run the Canada GST/HST calculator for province-based totals →