The small supplier definition is important to Canadian small businesses because whether or not your business qualifies as a small supplier determines whether or not you have to register for, collect and remit the GST/HST.
For businesses, the Canada Revenue Agency's small supplier definition states that to qualify as a small supplier, your total taxable revenues (before expenses) from all your businesses are $30,000 or less in the last four consecutive calendar quarters and in any single calendar quarter.
Now it's not quite as simple as it sounds. To determine if you fit the small supplier definition, making $30,000 or less annually, you have to include your worldwide revenues from your sales of goods and services that are subject to GST/HST, which includes zero-rated sales and supplies.
You also have to include revenues of any of your associates. You have to exclude financial services, goodwill , and sales of capital property.
For examples of how to calculate the limit to determine if you are a small supplier, see the Canada Revenue Agency's Small Supplier Limit Calculation page.
Note that even if you are a small supplier, you may still want to register for the GST voluntarily.
(Note, too, that this small supplier definition applies only to for-profit businesses. The small supplier threshold for charities and other public service bodies is different; to qualify as a small supplier, a charity or other public service body's revenues from worldwide taxable supplies (not including sales of capital property and financial services) must be equal to or less than $50,000 in the current calendar quarter and over the preceding four consecutive calendar quarters (Canada Revenue Agency).)