HST/GST Registration in Ontario: When You Must Register (Small Supplier Rule)

One of the most common questions I get from new business owners in Ontario: “Do I need to register for HST/GST?” The answer depends on how much revenue your business earns—and there's a specific threshold you need to know about.

This post explains the small supplier rule, when registration becomes mandatory, why some businesses register voluntarily even when they don't have to, and what happens if you miss the deadline.

What is the small supplier rule?

In Canada, you're considered a small supplier if your total taxable revenue (before expenses) is $30,000 or less over the last four consecutive calendar quarters, or in any single calendar quarter.

As a small supplier, you are not required to register for HST/GST. You don't have to charge HST on your sales, and you don't have to file HST returns.

Key point: The $30,000 threshold is based on revenue, not profit. Your expenses don't factor into this calculation.

When does HST/GST registration become mandatory?

You must register for HST/GST when your total taxable revenue exceeds $30,000 in:

• Any single calendar quarter, OR
• The last four consecutive calendar quarters combined

Once you cross the $30,000 threshold, you are no longer a small supplier. You must register immediately—not at the end of the quarter, not at year-end.

Important: “Immediately” means within 29 days of the day you exceed the threshold. From that point forward, you must charge HST on your taxable sales.

Who this applies to

This applies to anyone earning business income in Ontario, including:

• Sole proprietors and self-employed individuals
• Incorporated small businesses
• Contractors and freelancers
• Side-hustle earners approaching the threshold
• Uber/Lyft drivers and gig workers
• Online sellers and e-commerce businesses

Should you register voluntarily (even under $30,000)?

Even if you're under the $30,000 threshold, you can choose to register voluntarily. Some businesses do this because:

• You can claim ITCs (Input Tax Credits) — get back the HST you pay on business expenses like supplies, software, phone, and vehicle costs
• It looks more professional — some clients and vendors expect to see HST on invoices
• You're close to the threshold — registering early avoids a scramble when you cross $30,000
• Your expenses are high relative to revenue — if you're paying a lot of HST on purchases, you could get a refund

Voluntary registration isn't right for every business. If most of your clients are individuals (not businesses), adding 13% HST to your prices could make you less competitive. It depends on your situation.

How to register for HST/GST in Ontario

You can register through:

• CRA Business Registration Online — through your CRA My Business Account
• By phone — call the CRA Business Enquiries line
• Through your tax professional — we can handle the registration for you

When you register, CRA will assign you a Business Number (BN) with an RT extension for your GST/HST account, and they'll set your reporting period (monthly, quarterly, or annual).

What happens if you don't register on time?

If you exceed the $30,000 threshold and don't register, you could face:

• Back-dated HST liability — CRA can assess you for HST you should have been collecting from the date you exceeded the threshold
• Penalties and interest — on the HST you should have remitted
• Difficulty recovering — you may not be able to go back to clients and collect HST after the fact

This is one of the most expensive mistakes I see small business owners make. The HST comes out of your pocket if you didn't charge it to your clients.

Once you're registered: what's required

After registration, you must:

• Charge 13% HST on all taxable sales in Ontario
• Track HST collected and HST paid on business expenses
• File HST/GST returns on time (monthly, quarterly, or annually depending on your assigned period)
• Remit the difference (HST collected minus ITCs) to CRA
• Keep proper records and invoices

Common mistakes I see

• Not tracking revenue against the $30,000 threshold
• Thinking the threshold is based on profit (it's revenue)
• Waiting until year-end to register when the threshold was crossed mid-year
• Not charging HST after registration (absorbing it instead)
• Registering voluntarily without understanding the filing obligations
• Forgetting that the threshold applies to the last four quarters on a rolling basis
• Not keeping proper invoices (which you need to claim ITCs)

FAQs