If you run a business in Quebec, you’re not dealing with one sales tax system, you’re dealing with two, and they don’t always follow the same rules. GST is federal. QST is provincial, administered by Revenu Québec rather than the CRA, with its own registration threshold, its own return, and its own filing deadlines that don’t line up neatly with the federal ones.
Businesses outside Quebec selling to Quebec customers run into this too. Here’s what actually changes when QST enters the picture, and how to avoid filing the wrong tax at the wrong rate.
Two separate taxes, two separate agencies
Everywhere else in Canada, you’re dealing with GST alone, or HST where the province has harmonized its sales tax with the federal one. Quebec never harmonized. Instead, it runs GST at 5% and QST at 9.975% side by side, charged on top of each other on most goods and services.
The practical difference: your GST return goes to the CRA. Your QST return goes to Revenu Québec. They’re separate registrations, separate filings, and in some cases separate due dates, even though most Quebec businesses end up filing both around the same time each period.
QST is also calculated on the price before GST is added, not on top of the GST-inclusive total, so it isn’t quite as simple as stacking two flat percentages. On a $100 sale, GST adds $5.00, and QST adds $9.975 calculated on that same $100 base, for $14.975 in combined tax, not a compounded number. Most invoicing software handles this automatically, but it’s worth knowing the mechanics if you’re ever checking a calculation by hand.
| Tax | Rate | Administered by |
|---|---|---|
| GST | 5% | Canada Revenue Agency |
| QST | 9.975% | Revenu Québec |
| Combined, on a $100 sale | $14.98 in tax | Two returns |
Who actually needs to register for QST
The registration threshold mirrors the federal small supplier rule: once your worldwide taxable revenue (not just Quebec revenue) crosses $30,000 over four consecutive calendar quarters, you’re required to register for both GST and QST. Below that, registration is optional, though plenty of small businesses register early anyway so they can claim input tax credits on their own purchases.
One detail that trips up businesses outside Quebec: if you’re selling to Quebec customers and meet certain thresholds, you may need to register for QST even without a physical presence in the province. This became far more common after Quebec extended its digital sales tax rules to e-commerce and remote sellers.
An Ontario-based online retailer shipping regularly to Quebec customers, for instance, can find itself needing a QST registration years before it would ever need to think about registering in any other province, simply because Quebec’s rules for remote sellers are more assertive than most provincial sales tax regimes. It’s worth checking your Quebec sales volume specifically, not just your total national revenue, if a meaningful share of your customers are there.
Registering for GST does not automatically register you for QST, and vice versa. They’re separate applications through separate portals. A business that assumes one covers the other can end up unregistered, and non-compliant, for months without realizing it.
How input tax credits work on each side
Just like GST, QST has its own version of input tax credits, called Input Tax Refunds (ITRs) in Quebec. The mechanics are similar: you claim back the QST you paid on business purchases against the QST you collected from customers. But the two claims live on separate returns, so a purchase receipt needs to support both an ITC claim federally and an ITR claim provincially, and the documentation standard for each is checked independently if you’re ever reviewed.
This is one more reason a receipt with the tax breakdown clearly itemized matters more in Quebec than almost anywhere else in the country. A vague total doesn’t let you split GST from QST cleanly when it’s time to file.
Where QST and GST treat the same sale differently
Most goods and services are taxed the same way under both systems, but not all of them. A handful of categories, certain insurance products, some financial services, and specific health-related goods, are treated differently at the provincial level than at the federal one. A basic grocery item that’s zero-rated under GST is generally treated the same way under QST, but the overlap isn’t perfect across every category, and assuming the two systems always match on exemptions is a common source of small filing errors.
If your business sells anything outside the most common categories, a quick check against Revenu Québec’s current list is worth the ten minutes it takes, rather than assuming your GST treatment automatically applies on the QST side.
Filing frequency and how deadlines line up
Both GST and QST filing frequency (monthly, quarterly, or annual) are based on your revenue, and Revenu Québec generally assigns you the same frequency for QST as the CRA assigns for GST, since Revenu Québec collects both on behalf of most Quebec businesses. That’s the one piece of good alignment: most Quebec-registered businesses file GST and QST together, on one combined return, through Revenu Québec, rather than filing separately with each agency.
The exception is large businesses and certain financial institutions, which may need to file GST directly with the CRA. If you’re a typical small business, though, one combined filing through Revenu Québec usually covers both.
Set your GST/HST filing knowledge as a starting point, then layer QST on top rather than treating it as a completely separate system. Our plain-language GST/HST guide covers the federal side that QST builds on.
Common mistakes Quebec business owners make
- Charging GST but forgetting to add QST on top, especially on invoices copied from templates built for the rest of Canada.
- Registering for GST and assuming QST registration happened automatically.
- Missing that QST applies to some services GST doesn’t, and vice versa, in a handful of specific categories like certain insurance products.
- Using a bookkeeping tool that wasn’t built to track two tax rates on a single invoice line, which forces manual splitting every time.
- Assuming a Quebec client will handle QST on their end. If you’re the seller and you meet the registration threshold, the obligation to charge and remit it is yours, not theirs.
None of these are complicated once you know to watch for them. What makes QST genuinely tricky isn’t any single rule, it’s that Quebec businesses are effectively running two tax systems on autopilot for every transaction, and a small oversight in one doesn’t always show up until a return is filed and something doesn’t reconcile.
Keeping both taxes straight without doing it by hand
Running two tax systems on every invoice is exactly the kind of repetitive, error-prone task that eats up an owner’s Sunday afternoon. Nikmani tracks GST, HST, PST, and QST automatically as transactions come in, whichever combination applies to your province, so a Quebec sale gets both rates applied correctly without you doing the math by hand. Check the Silver plan if automatic tax tracking on every transaction is the piece currently costing you the most time.
If tax season itself still feels overwhelming beyond just the QST question, our small business tax season checklist walks through the full picture.