Most businesses in Quebec must charge two sales taxes: the federal GST (5%) and the Quebec QST (9.975%). Whether you have to register, and when, depends mainly on your revenue. Here is how it works, in plain language.
The short answer
You must register for the GST and the QST once your taxable sales go over $30,000, either in a single calendar quarter or over the last four calendar quarters combined. Below that, you are a "small supplier" and registration is optional.
How the $30,000 small supplier rule works
- Over four quarters: if your taxable sales over the last four consecutive calendar quarters go over $30,000, you must register. You start charging the taxes from the second month after the quarter in which you went over.
- In a single quarter: if you go over $30,000 in one calendar quarter, you stop being a small supplier immediately. You must charge GST and QST on the sale that put you over the limit and register right away.
- What counts: taxable sales, including zero-rated ones, from your business and associated businesses. Exempt sales, such as most residential rent and many health and financial services, do not count.
Who must register no matter what
Some businesses must register from their first dollar of revenue, including taxi and ride-sharing drivers. If you are unsure whether a special rule applies to you, check before you start invoicing.
How to register in Quebec
In Quebec, Revenu Québec handles both taxes for most businesses, so you register for the GST and the QST together with Revenu Québec, online or by form. You receive two numbers: a GST number tied to your federal business number, and a QST number. Both must appear on your invoices.
Should you register before you have to?
Voluntary registration can make sense, especially when you start up:
- You can claim back the GST and QST you pay on your business purchases (input tax credits and refunds).
- Business clients usually expect taxes on invoices and can claim them back themselves.
- In exchange, you must charge the taxes and file returns, even in quiet periods.
If most of your clients are individuals who can't claim the taxes back, staying a small supplier while you can may keep your prices lower.
How often you file
Your filing frequency depends on your annual taxable sales: annually for smaller businesses, quarterly for mid-size ones (above $1.5 million), and monthly above $6 million. You can often choose a more frequent schedule if you prefer.
Common mistakes
- Waiting until year-end to check your revenue, then owing taxes you never collected.
- Forgetting to put both tax numbers on invoices.
- Not keeping receipts for the input tax credits you claim.
We can register you and file for you
ABZ Accounting registers businesses for GST/QST, includes the returns in our bookkeeping service (from $175 per month), and can answer your specific question in a one-hour tax consultation. Rules change: this guide reflects the rules as of October 2026.