If you operate a sole proprietorship, a partnership, or a corporation that has gross sales over $30,000 in a fiscal year, you are required to register for and collect GST and QST. If your sales are less than $30,000, registration is optional.

If your income exceeds the $30,000 threshold for any four consecutive quarters, or in any quarter, you must register.

Sole proprietors operating more than one business must combine the income from all businesses when determining if they need to register.

If you are a public service body, such as a charity, you do not have to register for the GST/QST until your total revenues exceed $50,000.

You have 29 days from the time that your revenues reach $30,000 to register with Canada Customs and Revenue Agency (CCRA) so that you can charge GST/QST.

Pros and Cons
Often businesses that are not required to register for the GST/QST do so anyway.

On the positive side, registering early means you can claim back the GST/QST you paid for start-up purchases. For some businesses charging the GST/QST adds credibility, as customers won't know that the company is earning less than $30,000 a year.

On the down side, being registered means that you have extra paperwork to do. And of course, you also have to charge and remit the tax.