How to Back Out QST from a Quebec Invoice
Quebec is the only province that applies two separate taxes — federal GST (5%) and provincial QST (9.975%) — each calculated independently. The combined rate is 14.975%. When you have a tax-included total and need to work backwards to the pre-tax amount, you need the reverse formula.
The Reverse GST + QST Formula (Quebec 14.975%)
The formula is straightforward:
Pre-tax amount = Total ÷ 1.14975
Quebec's two taxes break down as follows:
- GST rate: 5% (federal)
- QST rate: 9.975% (provincial — applied to pre-tax amount, not on top of GST)
- Combined rate: 14.975%
- Formula: Pre-tax = Total ÷ 1.14975
- Total tax: Total − Pre-tax
Unlike some provinces where PST is calculated on the GST-included amount, Quebec's QST is applied to the pre-tax price only, so the combined divisor is simply 1.14975.
4 Worked Examples
| Total Paid | Pre-Tax Amount | GST (5%) | QST (9.975%) | Total Tax |
|---|---|---|---|---|
| $11.50 | $10.00 | $0.50 | $1.00 | $1.50 |
| $57.49 | $50.00 | $2.50 | $4.99 | $7.49 |
| $114.98 | $100.00 | $5.00 | $9.98 | $14.98 |
| $287.43 | $250.00 | $12.50 | $24.94 | $37.43 |
Example 1 — $11.50 total: $11.50 ÷ 1.14975 = $10.00 pre-tax. GST: $10.00 × 0.05 = $0.50. QST: $10.00 × 0.09975 = $1.00. Total tax: $1.50.
Example 2 — $57.49 total: $57.49 ÷ 1.14975 = $50.00 pre-tax. GST: $50.00 × 0.05 = $2.50. QST: $50.00 × 0.09975 = $4.99. Total tax: $7.49.
Example 3 — $114.98 total: $114.98 ÷ 1.14975 = $100.00 pre-tax. GST: $100.00 × 0.05 = $5.00. QST: $100.00 × 0.09975 = $9.98. Total tax: $14.98.
Example 4 — $287.43 total: $287.43 ÷ 1.14975 = $250.00 pre-tax. GST: $250.00 × 0.05 = $12.50. QST: $250.00 × 0.09975 = $24.94. Total tax: $37.43.
Skip the Math — Use the Calculator
Enter any Quebec invoice total into the free Quebec reverse GST + QST calculator and get the pre-tax amount, GST, and QST breakdown instantly — no division required.
What If You're a Business? (Input Tax Credits and ITRs)
If your business is registered for GST, you may be able to claim Input Tax Credits (ITCs) to recover the 5% GST paid on eligible business expenses. If you are registered for QST, you may be able to claim Input Tax Refunds (ITRs) to recover the 9.975% QST. Eligibility depends on your registration status and the nature of the expense — consult a tax professional for advice specific to your situation.
Quebec Sales Tax Exemptions
Not every Quebec purchase includes GST and QST. Common exempt and zero-rated items include:
- Basic groceries
- Prescription drugs
- Most medical devices
- Books (QST-exempt only; GST still applies)
If an item is exempt, there is no tax to back out — do not apply the ÷ 1.14975 formula to those totals.
Use the free Quebec reverse GST + QST calculator to extract GST and QST from any Quebec total instantly.
For the full Quebec tax reference including common amounts table and ITC/ITR rules, see the Quebec Province Tax Guide.
Calculations are arithmetic estimations only and do not constitute formal tax or corporate auditing advice. All figures must be verified against current CRA guidelines before filing.