Calculate Quebec GST and QST on a taxable amount, or extract them from a tax-inclusive total. Both taxes are calculated from the same pre-tax base.
GST = base × 5%. QST = base × 9.975%. Combined total = base × 1.14975. Reverse calculation: base = total / 1.14975.
On CAD 100 before tax, GST is CAD 5 and QST is CAD 9.975 before rounding. The combined total rounds to CAD 114.98.
Quebec QST is not a universal Canadian PST rate. Other provinces can use HST, another PST, or GST alone. Exemptions and zero-rated supplies are not assessed. Separately rounded tax lines may differ by a cent from a combined calculation.
References support the identified formula, unit or jurisdiction. They do not imply endorsement of this site. Check the original document for current conditions and exceptions.
Editorial responsibility: Nicolas Belotti · Methods and testing · Report an error
English edition: 16 September 2026.