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

If you're self-employed or running a small business in Ontario, HST registration is one of the easiest places to accidentally mess up—because the rules sound simple, but the timing catches people.

This post breaks down the small supplier rule in plain English so you know when you must register, when you should register early, and what to track.

What is the “small supplier” rule?

In Canada, you're generally considered a small supplier if your taxable revenues are $30,000 or less over a specific period (explained below). If you're a small supplier, you do not have to register for HST/GST.

But once you cross the threshold, registration becomes mandatory.

The $30,000 threshold (what counts and what doesn't)

What counts toward the $30,000?

• Most taxable sales (including zero-rated sales)
• Business income from taxable goods/services

What usually does NOT count (common examples)

• Some exempt supplies (depends on the situation)
• Pure reimbursements (if structured properly)
• Personal income not related to the business

If you're not sure what's taxable vs exempt in your situation, that's exactly where people get tripped up.

The timing: how the threshold is measured

This is the part that matters most.

You look at your taxable revenues over:

• A single calendar quarter, OR
• The last 4 consecutive calendar quarters combined

If you exceed $30,000, you may be required to register.

Scenario A: You exceed $30,000 in one quarter

If your taxable revenues go over $30,000 in a single calendar quarter, you generally stop being a small supplier at the end of that quarter and must register starting the next period.

Scenario B: You exceed $30,000 over 4 consecutive quarters

If your total taxable revenues over the last 4 consecutive calendar quarters exceeds $30,000, you generally stop being a small supplier at the end of the month following the quarter where you crossed the threshold.

(Yes, it's annoying. That's why tracking matters.)

When you should register early (even if you're under $30,000)

Sometimes registering early is smart:

• You have business expenses and want to claim ITCs (input tax credits)
• Your clients are businesses who can claim the HST back anyway
• You're clearly trending upward and will cross $30,000 soon
• You want to look more established (not a tax reason, but it's real)

But registering early also means you must charge, collect, and remit HST properly—so don't do it casually.

What happens after you register?

Once registered, you must:

• Charge HST on taxable sales (Ontario is generally 13%)
• Track HST collected vs HST paid on expenses (ITCs)
• File HST returns on time (annual/quarterly/monthly depending on your setup)
• Keep clean invoices and bookkeeping

The biggest mistake I see: people register, start charging HST… and then forget to set it aside. That becomes a cash-flow problem fast.

Quick checklist: do you need to register right now?

You may need to register if:

• Your taxable revenues are close to or above $30,000, AND
• You haven't been tracking by quarter, AND
• You're not sure what counts as taxable revenue

If you're even slightly unsure, it's worth checking before CRA checks for you.

FAQs