GST/HST registration for small businesses: when, how, and what it costs to get it wrong.

If your business made more than $30,000 in taxable revenue over the last four consecutive calendar quarters, or in a single quarter, you have to register for the GST/HST. You have 29 days to apply once you cross the line. After that, the Canada Revenue Agency (CRA) expects you to charge tax on your sales, file returns, and remit the difference. Miss the window and you end up owing tax you never collected, plus interest.

That is the rule. The interesting question is what to do well before you get there, and how to register without making your bookkeeping harder than it needs to be.

What "small supplier" actually means

You probably already know, but the CRA uses the term "small supplier" to describe a business that does not yet have to register for the GST/HST. You are a small supplier as long as your worldwide taxable revenue (the kind of sales that would have tax on them if you were registered) stays at or below $30,000 over four consecutive calendar quarters, and at or below $30,000 in any single quarter.

A few specifics that trip people up:

• The four quarters are calendar quarters (January to March, April to June, July to September, October to December), not your fiscal year.
• The number is gross revenue, before expenses, and includes the revenue of any associated businesses you control.
• It excludes the sale of capital property (think equipment or real estate), goodwill from selling a business, and financial services.
• For public service bodies (charities, qualifying non-profits, some municipalities), the threshold is $50,000.

Two ways to lose small-supplier status, and they behave differently.

1. The rolling four-quarter test. Add up taxable revenue across the most recent four calendar quarters. If the total is over $30,000, you stop being a small supplier at the end of the month following the quarter you crossed in. You then have 29 days to register.
2. The single-quarter test. If you make more than $30,000 in any single calendar quarter, you stop being a small supplier immediately, on the day you crossed. Effective date of registration is that day. You have 29 days to apply.

The single-quarter trigger is the one that catches founders off guard. A consulting business that books a single $40,000 project in March is no longer a small supplier as of the date that invoice pushes them past $30,000, even if the previous twelve months added up to almost nothing.

When you must register

Three situations force registration regardless of revenue:

• Taxi and commercial ride-share drivers. If you drive a taxi or work through a ride-share platform like Uber or Lyft, you have to register from day one. The small-supplier rule does not apply.
• Non-residents selling certain things in Canada. Non-residents who sell admissions to events in Canada, or who sell taxable digital products and services to Canadian consumers above $30,000, have specific registration rules under the CRA's digital-economy measures (in effect since July 2021).
• Voluntary registration. Anyone carrying on a commercial activity in Canada can register voluntarily, even below the threshold. More on that below.

Everyone else: the trigger is the $30,000 test, and the clock is 29 days from the date you cross it.

Should you register before you hit $30,000?

This is the question most small business guides skip. The default assumption is that you delay registration as long as possible to avoid charging your customers tax. That logic only works if your customers are end consumers who cannot claim input tax credits. For most B2B businesses, it is the wrong instinct.

Here is the trade-off.

The case for waiting until you have to register: you do not have to charge tax, which makes your prices look five to 15 percent lower than a registered competitor to a non-registered buyer. You also avoid the administrative cost of filing returns.

The case for registering voluntarily before $30,000:

• You recover the GST/HST on your business purchases. Every dollar of tax you pay on software, professional services, equipment, and supplies becomes an input tax credit you can claim back. Below the threshold, that tax is a pure cost.
• Your B2B customers do not care. A business that is itself registered claims the tax you charge them as an input tax credit. The tax is a wash for them. Charging it does not make you less competitive.
• It signals legitimacy. A GST/HST number on your invoices is one of the small visual cues that you are a real business, not a side hustle.
• It removes a future cliff. If you know you are going to cross $30,000 this year, registering now means you do not scramble through the 29-day window later, and you do not have to reissue invoices or chase customers for tax you forgot to charge.

The simple version: if you sell mostly to other registered businesses, register early. If you sell mostly to consumers and you are nowhere near $30,000, wait.

How to register, step by step

Registration is free and reasonably fast.

1. Get a Business Number (BN) if you do not already have one. Incorporated businesses get one when they incorporate. Sole proprietors can apply through CRA's Business Registration Online.
2. Choose your effective date of registration. If you are registering because you crossed the threshold, the effective date is the day you crossed (single-quarter trigger) or the start of the month following the quarter you crossed in (rolling test). If you are registering voluntarily, you can pick a date up to 30 days in the past.
3. Apply for a GST/HST account. Use CRA's Business Registration Online, call 1-800-959-5525, or file Form RC1. Most small businesses do this online in under 20 minutes.
4. Pick a reporting period. The CRA assigns one by default based on your revenue, but you can elect to file more frequently (see below).
5. Start charging tax on the effective date. From that day forward, every taxable invoice needs to show the tax, the rate, and your GST/HST number.

Which rate do you charge?

You charge the rate of the province where the supply is made, which usually means the province where your customer is located, not where you are. This is the part of the system that surprises businesses selling across provinces.

Current GST/HST rates (as of 2026):

The CRA publishes detailed place-of-supply rules for goods, services, intangibles, and real property. The short version, for most small services businesses: charge the rate where the customer is. An Ontario consultant invoicing a Halifax client charges 14 percent Nova Scotia HST, not 13 percent Ontario HST.

Reporting frequency: annual, quarterly, or monthly?

Once registered, you file GST/HST returns on a schedule the CRA assigns based on your taxable revenue. You can always elect to file more often, but you cannot elect to file less often than the threshold requires.

Most small businesses sit in the first row. The CRA will default you to annual filing, with quarterly instalment payments due if your net tax for the prior year was $3,000 or more.

Elect quarterly filing even if you qualify for annual. It surfaces problems four times a year instead of once, makes cash flow easier to predict, and forces a bookkeeping rhythm that catches errors early. The administrative cost of four filings instead of one is small once your books are clean.

What it costs to get this wrong

The two most common GST/HST mistakes carry real consequences.

Mistake one: missing the 29-day window. If the CRA decides you should have been registered, they will assign an effective date in the past. You will owe the tax you should have collected on every taxable sale since then, even if you never charged it. You can try to invoice customers retroactively, but many will refuse or have moved on. The tax then comes out of your margin. Add interest from the day each return was due, plus late-filing penalties.

Mistake two: forgetting that the threshold is rolling, not annual. The four-quarter test rolls forward every quarter. A business that did $25,000 in Q4 of 2025 and $10,000 in Q1 of 2026 is over the threshold (combined $35,000 across the four-quarter window that ends March 31, 2026), even if the calendar year totals look fine. The CRA does not care about your fiscal year here.

If you are unsure where you sit, the safest move is to pull your last four calendar quarters of taxable revenue from your bookkeeping software and add them up. If you are within 80 percent of $30,000, it is time to plan registration, not delay it.

You probably already know, but most of the businesses we onboard at Numinor cross the threshold without realizing it, then spend the first 90 days of the engagement cleaning up the back-tax position. The cleanup is not hard. The interest is not the end of the world. But it is avoidable, and the fix is almost always "register a quarter earlier." If you are behind on the books that would tell you where you stand, our catch-up bookkeeping process gets that current in about 30 days.

Sources and further reading