Reverse Sales Tax Calculator (Quebec GST/QST)
You have a $114.98 total and need to know how much of it is GST, QST and pre-tax amount? Divide by 1.14975. Enter the total below and the calculator breaks out all three figures instantly, in your browser, with no signup.
Enter the total amount paid, taxes included.
- GST included (5%)
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- QST included (9.975%)
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- Amount before taxes
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InnoBooks works out the tax on every invoice and produces your GST/QST summary. Create my free account →
This tool is provided for information purposes only and is not a substitute for professional tax advice.
Frequently asked questions
How do I calculate the pre-tax amount from a total?
Divide the total by 1.14975. For example, $114.98 ÷ 1.14975 = $100.00 before taxes. This calculator applies the formula and breaks out the GST and QST included.
What is the reverse sales tax formula in Quebec?
GST included = total × 0.05 ÷ 1.14975. QST included = total × 0.09975 ÷ 1.14975. Pre-tax amount = total − GST − QST. Calculating the taxes first guarantees that the three amounts add up to exactly the total you entered, with no one-cent discrepancy.
Why divide by 1.14975 instead of subtracting 14.975%?
Because the percentage applies to the pre-tax amount, not to the total. Subtracting 14.975% from a $114.98 total would give $97.76, which is wrong. Division is the only exact method.
When do you need a reverse sales tax calculation?
Mostly to record a receipt that only shows a total, to check a supplier invoice, or to claim input tax credits (ITC) and input tax refunds (ITR) on an expense.
Does this work if only GST applies?
No — this calculator assumes both GST and QST apply, which is the case for most taxable supplies in Québec. For a purchase outside Québec, use the rate of the relevant province.
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