GST, HST, PST, and QST describe Canadian sales-tax systems that change which rate belongs in a reverse tax calculation. GST is federal, HST combines federal and provincial tax, PST is separate provincial tax, and QST applies in Québec. A tax-inclusive Canadian receipt can use one combined rate or separate tax lines; reverse calculation must match the printed tax structure before extracting the included tax. Province and transaction date set the rate.
What Are GST, HST, PST, and QST?
These taxes are consumption taxes, meaning they generally apply to taxable supplies of goods and services.
| Tax | Meaning | Basic role |
|---|---|---|
| GST | Goods and Services Tax | Federal tax |
| HST | Harmonized Sales Tax | Combined federal and provincial tax |
| PST | Provincial Sales Tax | Provincial tax in some provinces |
| QST | Québec Sales Tax | Québec provincial sales tax |
The reverse tax method depends on whether the taxes are shown separately, combined, or included in one final total.
GST Explained
GST is Canada’s federal goods and services tax. CRA guidance states that the rate to charge depends on the place of supply and that zero-rated supplies have a 0 percent GST/HST rate throughout Canada. It gives basic groceries as an example of a zero-rated supply.
For reverse tax:
| GST situation | Calculation approach |
|---|---|
| GST only included | Divide by GST multiplier |
| GST shown separately | Subtract or verify |
| GST plus PST | Check whether both apply and how |
| Zero-rated supply | No GST amount to remove |
GST Reverse Tax Formula
If GST is the only tax included:
Pre-tax amount = GST-inclusive total / 1.05
Included GST:
GST = GST-inclusive total - pre-tax amount
Example:
210.00 / 1.05 = 200.00
210.00 - 200.00 = 10.00
HST Explained
HST combines GST and a provincial component into one harmonized rate in participating provinces. CRA guidance says that if HST applies, the total HST rate should be shown rather than the federal and provincial parts separately.
CRA guidance also notes that Nova Scotia decreased the provincial portion of HST effective April 1, 2025, resulting in a 14 percent HST rate in Nova Scotia.
For reverse tax, HST is usually treated as one combined rate:
Pre-tax amount = HST-inclusive total / (1 + HST rate / 100)
HST Reverse Tax Formula
If the HST rate is 13 percent:
Pre-tax amount = HST-inclusive total / 1.13
If the HST rate is 14 percent:
Pre-tax amount = HST-inclusive total / 1.14
Use the rate that applies to the place of supply and transaction date.
PST Explained
PST is provincial sales tax. It is separate from GST in provinces that use PST rather than HST. PST rules vary by province.
CRA guidance notes that if PST is charged in the place of supply, GST is calculated on the price without the PST. This matters because GST and PST may not always be a single compounded rate.
For reverse tax, check whether the total includes:
| Tax setup | Reverse-tax approach |
|---|---|
| GST only | Use GST rate |
| PST only | Use PST rate if applicable |
| GST and PST separately | Use additive or line-based method |
| Tax shown by line | Reverse each line or group |
PST and GST Are Not Always One Simple Rate
When GST and PST are both charged, verify the calculation base. If both are calculated on the same pre-tax price, an additive combined rate can work as a math shortcut. If one tax is calculated differently, or if exemptions differ, separate the lines.
| Situation | Method |
|---|---|
| GST and PST on same base | Add rates as a shortcut |
| GST applies but PST exempt | Reverse GST only |
| PST applies but GST zero-rated | Reverse PST only if included |
| Different bases | Calculate separately |
QST Explained
QST is Québec sales tax. Revenu Québec states that GST is calculated at 5 percent on the selling price, and QST is calculated at 9.975 percent on the selling price excluding GST.
That means a simple Québec GST and QST example can use:
5 percent + 9.975 percent = 14.975 percent
This is not because QST disappears into GST. It is because QST is calculated on the selling price excluding GST under the cited Revenu Québec rule.
QST Reverse Tax Formula
For a basic Québec example where GST at 5 percent and QST at 9.975 percent both apply to the selling price:
Combined rate = 14.975 percent
Pre-tax amount = Total / 1.14975
Then:
Included tax = Total - pre-tax amount
This formula should be used only when the same base and cited rule apply.
GST vs HST vs PST vs QST
| Tax | Federal or provincial | Usually shown as | Reverse-tax concern |
|---|---|---|---|
| GST | Federal | Separate tax | May combine with PST |
| HST | Combined federal-provincial | One total HST rate | Use total HST rate |
| PST | Provincial | Separate provincial tax | Rules vary |
| QST | Québec provincial | Separate provincial tax | Combine carefully with GST |
Canadian Tax Entity Map
| Entity | Role |
|---|---|
| Supply | Good, service, lease, or other taxable supply |
| Place of supply | Determines which province or territory rate applies |
| GST | Federal component |
| HST | Combined federal and provincial component |
| PST | Separate provincial component |
| QST | Québec provincial component |
| Zero-rated supply | Taxed at 0 percent |
| Exempt supply | No GST/HST charged under exempt rule |
The reverse calculation starts only after these entities are classified.
Place of Supply
CRA guidance says the rate to charge depends on place of supply, meaning where the sale, lease, or other supply is considered to be made.
This matters for online and delivered orders.
CRA gives examples where delivery location or pickup location changes the tax charged. In one example, a laptop delivered to Nova Scotia uses Nova Scotia HST, while customer pickup in Manitoba uses GST and Manitoba PST.
For reverse tax:
| Scenario | Rate-selection issue |
|---|---|
| Pick up in store | Store province may matter |
| Delivered to customer | Destination may matter |
| Digital service | Place-of-supply rules may apply |
| Cross-border sale | Import or export rules may apply |
| Zero-rated supply | Rate may be 0 percent |
Receipt and Invoice Display
CRA guidance says customers must be told if GST/HST is applied and whether GST/HST is included in the price or added separately. It also says receipts or invoices must show the GST/HST rate and amount paid or payable with GST/HST amount as separate lines, or clearly state that the total includes GST/HST.
For reverse tax, this means the receipt may give you one of three useful clues:
| Display | What to do |
|---|---|
| Tax shown separately | Verify by subtraction |
| Total says tax included | Reverse from total |
| HST rate shown | Use total HST rate |
Reverse Tax Example: GST Only
A GST-only example applies when the receipt contains only GST, such as a clean 5% GST amount in a GST-only context. Divide the GST-inclusive total by 1.05 to recover the pre-tax amount, then subtract to find GST. Do not use this example for HST, GST plus PST, or Quebec GST plus QST receipts.
Suppose a GST-inclusive total is 105.00 and the GST rate is 5 percent.
105.00 / 1.05 = 100.00
105.00 - 100.00 = 5.00
The pre-tax amount is 100.00 and the included GST is 5.00.
Reverse Tax Example: HST
An HST example applies when the receipt shows one harmonized tax line. Divide the HST-inclusive total by 1 plus the HST rate for the province and date. The important distinction is that HST is not just the 5% federal GST. It includes a provincial component inside one combined rate.
Suppose an HST-inclusive total is 114.00 and the HST rate is 14 percent.
114.00 / 1.14 = 100.00
114.00 - 100.00 = 14.00
The pre-tax amount is 100.00 and the included HST is 14.00.
Québec GST and QST Example
Suppose the selling price before tax is 100.00.
| Component | Amount |
|---|---|
| Selling price | 100.000 |
| GST at 5 percent | 5.000 |
| QST at 9.975 percent | 9.975 |
| Total | 114.975 |
Reverse calculation using additive combined rate:
114.975 / 1.14975 = 100.00
Included tax:
114.975 - 100.00 = 14.975
After cent rounding, receipt totals may vary by one cent depending on line-level calculations.
Reverse Tax Example: GST and PST
Suppose a total includes GST at 5 percent and PST at 7 percent, both calculated on the 100.00 selling price.
| Component | Amount |
|---|---|
| Selling price | 100.00 |
| GST at 5 percent | 5.00 |
| PST at 7 percent | 7.00 |
| Total | 112.00 |
Reverse using additive combined rate:
112.00 / 1.12 = 100.00
Use this only when both taxes are calculated on the same pre-tax base.
Example: Zero-Rated Supply
A zero-rated supply has a 0% rate for calculation purposes, so there is no tax amount to remove from the price. The gross and net amount are the same for reverse-tax arithmetic. Zero-rated and exempt can have different reporting meanings, but a reverse calculator should not remove GST, HST, PST, or QST from a zero-rated amount.
Suppose a receipt total is 50.00 for a zero-rated supply at 0 percent GST/HST.
50.00 / 1.00 = 50.00
Included tax:
50.00 - 50.00 = 0.00
Do not reverse a zero-rated supply with the standard GST rate. Zero-rated means the rate is 0 percent for the supply.
Decision Matrix for Canadian Reverse Tax
| Receipt or invoice situation | Reverse-tax action |
|---|---|
| GST only included | Divide by 1.05 |
| HST included | Divide by total HST multiplier |
| GST and PST shown separately | Check bases, then combine or separate |
| GST and QST in Québec | Use 14.975 percent only when the basic rule applies |
| Zero-rated supply | Use 0 percent |
| Exempt supply | Do not remove tax |
| Mixed taxable and zero-rated items | Split first |
| Delivered order | Check place of supply |
Common Mistakes
Common mistakes include treating HST as GST-only, ignoring PST or QST, applying a combined rate to exempt lines, using one province's rate for another province, and removing tax from zero-rated supplies. The fix is to identify tax label, province, taxable base, and receipt date before calculating.
The practical mistake pattern is label confusion. GST, HST, PST, and QST are related but not interchangeable. A Canadian receipt may need a GST-only formula, an HST formula, a GST plus PST formula, or a GST plus QST formula. The tax label and province should be resolved before the calculator asks for a rate.
Treating HST as Separate GST and PST
HST is a harmonized tax shown as a total HST rate when it applies.
Compounding GST and QST Incorrectly
Use the official rule. Revenu Québec states QST is calculated on selling price excluding GST.
Ignoring Place of Supply
Delivery and pickup location can change the applicable tax.
Reversing Zero-Rated Supplies
If the rate is 0 percent, there is no tax amount to remove.
Using One Rate for Mixed Items
Separate taxable, zero-rated, and exempt supplies.
What This Page Does Not Cover
| Topic | Better page |
|---|---|
| Québec calculator page | Québec Reverse Sales Tax Calculator |
| Choosing a rate | How to Choose the Correct Tax Rate |
| Multiple taxes formula | Reverse Formula for Multiple and Stacked Taxes |
| Canadian province pages | Province-specific calculator pages |
Frequently Asked Questions
What is the difference between GST and HST?
GST is federal. HST combines the federal GST with a provincial component into one harmonized tax in participating provinces.
What is PST?
PST is provincial sales tax used by some provinces outside the HST system.
What is QST?
QST is Québec sales tax. It is charged along with GST on many Québec supplies.
How do I reverse GST?
Divide the GST-inclusive total by 1 + GST rate / 100, then subtract the pre-tax amount from the total.
How do I reverse GST and QST in Québec?
For the cited Revenu Québec basic rule, use a combined additive rate of 14.975 percent when both GST at 5 percent and QST at 9.975 percent apply to the same selling price.
Can I use one Canadian rate for every province?
No. Place of supply, province, tax type, and supply type matter.
Sources
These sources support Canadian tax label and rate context. The formulas on this page come from the arithmetic relationship between pre-tax amount, tax rate, tax amount, and tax-inclusive total. Use CRA, Revenu Quebec, and provincial tax authority guidance for taxability, registration, filing, and rate decisions.