Every week a business owner tells us some version of the same story: sales took off faster than expected, someone mentioned the $30,000 rule, and now they’re not sure if they’re offside with the CRA. The good news is that GST/HST is one of the simpler things you’ll deal with as a Canadian business owner, once someone explains it without the jargon. This is that explanation.
What a GST number actually is
Your GST number is your nine-digit CRA business number with “RT0001” on the end. Registering for GST/HST doesn’t create a new identity for your business; it activates a program account on the business number you already have (or triggers the CRA to issue you one). Once registered, you charge GST or HST on your sales, remit it to the CRA on a schedule, and claim back the GST/HST you pay on business expenses.
That last part is the piece new registrants consistently miss, and it’s worth money. More below.
The $30,000 rule, properly explained
You must register once your worldwide taxable sales pass $30,000 over four consecutive calendar quarters, or in a single quarter. Under that line, you’re a “small supplier” and registration is optional.
Two details trip people up:
It’s a rolling test, not a calendar-year test. You check the current quarter plus the previous three. Cross $30,000 across that window and the clock starts: exceed it over four rolling quarters and you must register within 29 days of the sale that tipped you over the threshold, in the month following the end of that window. Blow past $30,000 inside one single quarter and you’re registered effective the sale that crossed the line.
It’s revenue, not profit. A reseller doing $35,000 in sales on thin margins is over the threshold, even if they took home $6,000.
Miss the deadline and the CRA treats you as registered from the date you should have been, meaning you owe the GST/HST on sales you never collected it on. Out of your own pocket. This is the single most expensive GST mistake we see, and it’s entirely avoidable.
Should you register before you have to?
Often, yes. Voluntary registration below $30,000 makes sense when:
Your customers are businesses. They reclaim the GST/HST you charge, so it costs them nothing, and an unregistered supplier reads as “hobbyist” to procurement departments. Registration is cheap credibility.
You’re spending on setup. Equipment, inventory, professional fees, software: registered businesses claim back the GST/HST on all of it as input tax credits. Pre-revenue businesses investing heavily can recover thousands.
You sell zero-rated goods (exports, basic groceries): you charge 0 percent but still reclaim what you pay. Registration is nearly all upside.
The main reason to wait: your customers are consumers and your margins are tight. Registration makes your prices 5 to 15 percent higher to the public, or squeezes your margin by the same amount if you absorb it.
How to register (it takes about ten minutes)
The fastest route is CRA Business Registration Online, which issues your business number and GST/HST account together if you’re new. Phone registration through the CRA business line works too, as does mail for the patient. Quebec businesses register with Revenu Québec, which administers GST alongside QST.
Have on hand: your SIN (for sole proprietors) or corporation details, business activity description, and your estimated annual revenue. You’ll choose a reporting period; most small businesses default to annual filing, and you can elect quarterly if you prefer smaller, regular remittances or expect refunds.
What rate you charge
You charge based on your customer’s province, not yours. HST provinces (Ontario at 13 percent; Nova Scotia, New Brunswick, PEI and Newfoundland and Labrador at their combined rates) get HST. GST-only provinces and territories get 5 percent, with provincial sales tax handled separately where it applies (BC, Saskatchewan, Manitoba) and Quebec running its own QST system. Selling across provinces? Your invoicing or ecommerce platform should apply place-of-supply rates automatically, but spot-check it; misconfigured tax settings are a routine find in the bookkeeping cleanups our clients tell us about.
Input tax credits: the part that pays you
Every dollar of GST/HST your business pays on legitimate expenses comes back to you as an input tax credit, netted against what you’ve collected. Rent, fuel, equipment, software subscriptions, professional fees, the GST on financed equipment purchases: all claimable, provided you keep the receipts and the supplier’s GST number appears on invoices over the CRA’s documentation thresholds.
Practical implications that surprise people:
- A quarter where you invested heavily can produce a refund, not a bill.
- The quick method, an optional simplified calculation for smaller businesses, can leave service businesses with low expenses ahead of the standard method. Worth an hour with your accountant to compare.
- ITCs are one more reason the separate business bank account matters: clean records make claims defensible.
Filing, remitting, and the cash flow trap
Collected GST/HST is not your money. It’s the CRA’s, passing through your account. The businesses that get into GST trouble are almost never confused about the rules; they’ve spent the tax during a tight month and can’t remit when filing comes due. CRA penalties and interest compound quickly, and the CRA is a uniquely unpleasant creditor.
Two habits prevent it: move collected tax into a separate account weekly, and if a shortfall has already happened, deal with it before the deadline rather than after. Short-term working capital at commercial rates is consistently cheaper than CRA penalties plus the damage a tax debt does to every future funding application, because tax arrears are the first thing any lender asks about.
Frequently asked questions
Is a GST number the same as a business number? The GST number is your business number plus the RT0001 program identifier. One number, multiple program accounts: RT for GST/HST, RP for payroll, RC for corporate income tax. If you have a business number already, adding GST/HST takes minutes.
How much does it cost to get a GST number? Nothing. Registration is free. Paid “registration services” advertising online are middlemen filing a free form on your behalf.
Do I charge GST/HST to customers outside Canada? Exports are generally zero-rated: you charge 0 percent but still claim your input tax credits. Keep evidence of export.
What happens if I never register and stay under $30,000? Nothing; that’s the small supplier rule working as intended. Just keep watching the rolling four-quarter total, because the obligation arrives with the sales, not with a CRA letter.
GST registration is a ten-minute job. GST discipline is a habit. Get both right early and the tax becomes background admin instead of a landmine. And if a remittance deadline is bearing down on a tight month, talk to us before it becomes a CRA problem.
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