How this instrument works
Quebec is the only Canadian province that still administers its own provincial sales tax rather than folding it into a single blended rate. The five Harmonized Sales Tax provinces show one combined line on a receipt; Quebec shows two, because the federal 5% Goods and Services Tax (GST) and the provincial 9.975% Quebec Sales Tax (QST) are remitted to two different governments — the Canada Revenue Agency and Revenu Québec — and each is calculated independently on the same pre-tax amount rather than one applying on top of the other.
That last detail was not always true. Before January 1, 2013, Quebec computed QST on a price that already included GST, a tax-on-tax arrangement that pushed the effective combined rate above the sum of the two headline percentages. Revenu Québec harmonized the QST base with the federal base that year, so both taxes now sit side by side on the identical pre-tax figure: 5% and 9.975% of the same number, added together rather than compounded. A formula or old spreadsheet built before that change will overstate the tax owed today.
Who reaches for this arithmetic tends to be narrow: a Quebec-registered small business pricing an invoice, a freelancer confirming what to charge a Montreal client, or an out-of-province online seller who has crossed the roughly $30,000 threshold that obliges non-resident sellers to register for and charge QST on sales into Quebec even without a storefront there. None of those situations change the multiplication — they change only whether a given seller is required to run it at all.
- Enter the pre-tax price into Amount, $ — the figure before either tax line is added.
- Read GST (federal, 5%) for the fixed federal share, calculated on that same pre-tax amount.
- Read QST (Quebec, 9.975%) for the provincial share, calculated independently on the identical base rather than on the GST-inclusive price.
- Check Total including GST + QST for the figure that actually leaves the buyer's account or lands on the invoice.
- Change Amount, $ to see both tax lines and the total move together while the two rates stay fixed.
Worked example — a $1,000 purchase in Quebec
Enter $1,000 into Amount, $. The federal rate is fixed at 5%, so GST = 1,000 × 5 ÷ 100 = $50.00 exactly, and that figure appears in GST (federal, 5%). The provincial rate is fixed at 9.975%, so QST = 1,000 × 9.975 ÷ 100 = $99.75, appearing in QST (Quebec, 9.975%) — calculated on the same $1,000 the GST used, not stacked on top of a GST-inclusive figure.
Total including GST + QST adds all three: 1,000 + 50.00 + 99.75 = $1,149.75, which is what a Quebec buyer actually pays or a Quebec-registered seller actually invoices. Double the purchase to $2,000 and both tax lines double with it — $100.00 of GST and $199.50 of QST — because each rate is a fixed percentage of whatever pre-tax figure sits in Amount, $, added rather than multiplied against each other.
Questions
Why does Quebec charge two separate sales taxes?
Quebec is the only province that still administers its own sales tax through a separate agency, Revenu Québec, rather than folding it into a single blended rate the way the five Harmonized Sales Tax provinces do. The federal GST and Quebec's QST are calculated independently and shown as two lines, which is why a Quebec receipt lists 5% and 9.975% separately instead of one combined percentage.
Is QST calculated on top of the GST-inclusive price?
No — not since January 1, 2013. Before that date Quebec computed QST on a price that already included GST, a tax-on-tax effect that made the province's true combined rate higher than 5% plus 9.975% suggests. Revenu Québec harmonized the QST base with the federal base that year, so both taxes now apply independently to the same pre-tax amount, exactly as this sheet computes them.
Do out-of-province online sellers have to charge QST?
Often yes. Since 2019, a business outside Quebec that sells taxable goods or digital services to consumers there and passes roughly $30,000 in such sales must register for QST and charge it alongside GST, even with no physical presence in the province. This sheet computes the tax on one transaction; whether a specific seller must register at all is a separate threshold question, not an arithmetic one.
What is the combined tax rate on a Quebec purchase?
5% GST plus 9.975% QST works out to 14.975% of the pre-tax price, not a round 15%, because both rates apply to the same base rather than one compounding on the other. On a $1,000 purchase that is $149.75 of combined tax, split as $50.00 GST and $99.75 QST — kept on separate lines here because the two amounts are remitted to two different governments.
Why doesn't my receipt match 5% and 9.975% exactly?
Rounding, almost always. Each tax line is rounded to the cent on its own — 9.975% of an odd figure like $19.99 works out to $1.99425, printed as $1.99 — so summing two already-rounded lines can land a cent away from rounding the combined 14.975% just once. Both routes are legitimate; Quebec retailers round each tax separately, which is the calculation this sheet performs.
Can a Quebec business recover the GST and QST it pays on supplies?
A registered business generally can, through input tax credits for GST and input tax refunds for QST — separate claims filed with the Canada Revenue Agency and Revenu Québec respectively, since the two taxes fund different governments despite sharing a base. A final consumer files no such claim, so the tax on a personal purchase is the amount that sticks; this sheet shows what is owed on one line, not what a business later reclaims.
References
Read this first: This instrument shows arithmetic, not advice. Real offers add fees, taxes and terms that vary by lender and place — verify the figures against your actual paperwork before deciding anything.