GST/QST calculator

Multiply the pre-tax amount by 5% for the GST and by 9.975% for the QST, round each tax to the cent, then add everything up. For $100: $5.00 of GST and $9.98 of QST, for a total of $114.98.

Divide the total by 1.14975 to get the pre-tax amount, then calculate each tax on that amount. For $114.98: $100.00 before taxes. The calculator checks that the sum gives back your exact total.

No. Since January 1, 2013, the QST is calculated on the pre-tax amount, like the GST. The combined rate is therefore 14.975%.

Because each tax is rounded to the cent, some totals match no pre-tax price. For example, no price gives exactly $20.00 with taxes included: $17.39 gives $19.99 and $17.40 gives $20.01. The calculator then shows the closest price and the one-cent difference.

If your taxable sales exceed $30,000 in a calendar quarter or over four consecutive calendar quarters, you must register for the GST and QST and collect the taxes. Below that threshold, you are a small supplier and registration is optional. Some services, including many health services, are exempt: check your situation with Revenu Québec.

Your GST and QST registration numbers, the pre-tax amount and the amount of each tax. AssisTime adds them to every invoice automatically and includes them in your sales tax report.