Practical guide · GST/QST
GST and QST in Odoo: getting them right
An invoice with the wrong tax means an unhappy customer and a painful correction. Here’s how Odoo handles GST and QST, and what to check before issuing your first invoice.
Why this configuration deserves your attention
Odoo is international software. At installation, it offers a set of taxes based on the chosen country, but nothing guarantees it matches your exact situation: rates applied, tax accounts, registration numbers shown, handling of sales outside Quebec.
These settings are made once, at the start. Corrected after three months of invoicing, they require reworking entries already posted — it can be done, but it’s work nobody likes to bill or pay for.
How Odoo handles GST and QST
Odoo applies taxes based on a fiscal position assigned to the customer, and default taxes assigned to the product. For a Quebec customer, the fiscal position applies both taxes; for an Ontario customer, it replaces them with HST.
Each tax points to a separate account, which lets you pull, in one click, the amounts collected and paid for each tax over a given period. That’s what will make your return simple later on.
The right reflex: configure fiscal positions before creating your customers, so each record starts with the right one.
The compound calculation trap
It’s the most common mistake, and it comes from an old habit. Until 2012, QST was calculated on the amount including GST. That’s no longer the case: today both taxes are calculated on the same amount, the pre-tax amount.
Odoo lets you enable compound (cascading) calculation — useful elsewhere in the world, but definitely not to be checked here. A QST calculated in cascade creates a gap of a few dollars per invoice, small enough to go unnoticed for a long time and real enough to throw off your returns.
To check: issue a $100 test invoice. You should get $5.00 of GST, $9.975 of QST and a total of $114.98. Any other result points to a configuration problem.
Quebec special cases
A few situations that require an explicit setting:
- Sales in another province — the fiscal position must apply HST or GST alone, depending on the province of delivery.
- Sales abroad — zero-rated, but they must still appear in your returns.
- Exempt products and services — certain health, education or financial services. A 0% tax is not the same thing as no tax.
- Unregistered small supplier — below the $30,000 threshold, you don’t charge taxes. Odoo must be configured accordingly, and reconfigured the day you register.
Your registration numbers on invoices
Your GST and QST numbers must appear on any invoice where you charge taxes: that’s what allows your customer to claim their input tax credits. An invoice without these numbers may be refused, and they’ll come back to you.
In Odoo, these numbers are entered in your company record and then appear automatically on documents. Check it once, by looking at a real printed invoice — not just the on-screen preview.
Producing your returns from Odoo
Once taxes are properly configured, Odoo produces a tax report for the period of your choice: amounts collected, amounts paid, the balance to remit. That report feeds your return to Revenu Québec.
Odoo doesn’t file the return for you and doesn’t replace your accountant. It gives you reliable figures, which is already most of the work.
The mistakes we fix most often
- US configuration taxes left in place after a quick installation.
- Products created without a default tax, producing tax-free invoices without anyone noticing.
- Customers without a fiscal position, so taxed like Quebecers even outside the province.
- Registration numbers missing from the invoice template.
- Compound calculation turned on.
None of these mistakes is serious on its own. Together, they make a quarterly return painful and costly to reconstruct.
Have your configuration checked
Already have Odoo in place and doubts about your taxes? Write to us: a check usually takes less than an hour.