How to Register for an HST Number in Canada (For Startups)
You incorporated. You got a Business Number from the CRA. Now someone — a customer, an accountant, a lawyer — is asking for your HST number. These are not the same thing. Most Canadian founders conflate the Business Number with the HST registration, and the confusion usually surfaces at an inconvenient moment: when you need to invoice a customer, recover tax on a large purchase, or respond to a CRA inquiry.
Here is the plain-English version of how this works.
Your Business Number is not your HST number
When you incorporate federally under the CBCA, Corporations Canada automatically notifies the CRA, which issues a 9-digit Business Number (BN). This BN is your corporation’s CRA identifier. It is not, on its own, a GST/HST registration.
The GST/HST account is a separate program account added under the BN. Its identifier is your BN followed by “RT0001” — for example, 123456789 RT0001. That full string is what customers are asking for when they request your “HST number.” You do not have it until you have registered for the GST/HST program separately.
Other program accounts exist under the same BN structure — payroll (RP), corporate income tax (RC) — but the GST/HST account (RT) is the one most relevant to early-stage startups generating revenue.
When you must register
Registration is mandatory once your taxable revenues exceed $30,000in either a single calendar quarter or over four consecutive calendar quarters. The CRA calls this the “small supplier” threshold.
Once you cross the $30,000 threshold, you have approximately 29 days to register. That window is shorter than most founders expect, and the penalty for missing it is not merely administrative: the CRA can assess you for the GST/HST you should have been collecting, regardless of whether you actually collected it from customers. If you charged without remitting, you owe the tax. If you did not charge and did not collect, you still owe the tax — and your customers have no recourse to recover the input tax credits they would have otherwise been entitled to.
29 days after crossing $30,000
Once your taxable revenues exceed $30,000 in a single quarter or over the previous four consecutive quarters, you have 29 days to register for GST/HST. Miss this window and the CRA can assess unremitted tax on all taxable supplies made after you were required to register — including amounts you never collected.
Why you might want to register before you hit $30,000
Small suppliers can voluntarily register for GST/HST at any time, even before crossing the threshold. There is a real reason to do this early: input tax credits (ITCs).
As a registered business, you can claim ITCs to recover the GST/HST you paid on business expenses — legal fees, SaaS subscriptions, equipment, office costs. Before you register, that tax is just a cost. After you register, it is recoverable. For a pre-revenue startup with meaningful operating costs, early voluntary registration can mean recovering real money that would otherwise be lost.
The tradeoff is filing obligations. Once registered, you must file GST/HST returns on a schedule set by the CRA (quarterly for most early-stage companies), whether or not you collected any tax that period. Missing a return generates penalties. For a company still building its first product, adding a quarterly compliance obligation before it is necessary is a judgment call worth discussing with an accountant.
How to actually register
Since November 2025, the CRA no longer accepts new Business Number or program account registrations by phone. Registration is done through CRA Business Registration Online. The process:
- Log in to your CRA My Business Account (or register for one if you have not yet).
- Navigate to “Register a CRA program account” and select GST/HST.
- Provide your BN, incorporation details, and expected annual revenue.
- Choose your reporting period — annual, quarterly, or monthly. Most early-stage companies default to quarterly.
- Choose a GST/HST filing start date. This determines which period your first return covers.
Registration typically processes within a few business days. Once approved, you will receive your RT0001 account number, which is what goes on your invoices.
The Quebec exception
If your business is based in Quebec, the GST/HST administration works differently. Revenu Québec administers the GST/HST on behalf of the CRA for Quebec businesses, as well as the provincial QST (Québec Sales Tax). You register through Revenu Québec rather than the CRA, and you manage both taxes through the same registration. Non-Quebec businesses that make taxable supplies in Quebec may also have QST obligations worth reviewing with an accountant familiar with interprovincial tax.
The bottom line
Register when you cross $30,000 in taxable revenue — within 29 days, not at your leisure. Consider registering voluntarily early if your startup is spending meaningfully before generating revenue, so you can recover the GST/HST on those costs. When you register, you get a full HST number (BN + RT0001), not just the BN you received at incorporation.
If you are unsure whether a specific revenue stream is taxable under the GST/HST rules — some supplies are zero-rated or exempt — get a brief answer from an accountant before you start collecting or not collecting. The wrong assumption in either direction creates a problem that compounds over time.
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