Wondering about the business number and HST in Ontario? Here is the short version: a business number (BN) is the 9-digit ID the CRA uses for your business, and an HST account is one program account attached to it. You are legally required to register for HST once your taxable revenue passes $30,000, but you can also register voluntarily before then.
What is a CRA business number?
A business number (BN) is a unique 9-digit number the Canada Revenue Agency assigns to your business. Think of it as your company's file number across government: it identifies you to the CRA and to many provincial, territorial, municipal and other federal programs.
On its own, the 9-digit BN does not let you do much. The BN becomes useful when you add program accounts to it. Each program account tacks a two-letter code and a four-digit reference number onto the end of your BN, telling the CRA which activity you are reporting. For example, a BN with an HST account looks like 123456789 RT0001.
Business number program accounts — what each is for
Most small businesses only ever need one or two of these. Here is what the common program accounts cover.
| Program account | Suffix | What it is for |
|---|---|---|
| GST/HST | RT | Charging, collecting and remitting HST on your taxable sales |
| Payroll deductions | RP | Withholding and remitting income tax, CPP and EI when you have employees |
| Corporate income tax | RC | Filing and paying your corporation's income tax (corporations only) |
| Import-export | RM | Importing goods into or exporting goods out of Canada |
You add each account only when you actually need it. A solo consultant with no staff might only ever open an HST (RT) account. A corporation that hires its first employee later adds a payroll (RP) account to the same BN.
When must you register for HST?
This is the question most Ontario founders are really asking. The rule turns on the small-supplier threshold.
You are a small supplier — and not required to register — as long as your total worldwide revenue from taxable supplies stays $30,000 or less in a single calendar quarter and over the last four consecutive calendar quarters. Once you cross that line, you must register.
Specifically, you must register for HST when your taxable revenue exceeds $30,000:
- in a single calendar quarter, or
- over the previous four consecutive calendar quarters.
The threshold is based on revenue before expenses, and it counts your worldwide taxable sales, not just Ontario ones. Once you pass it, you have to register within 29 days of your effective date and start charging HST from that date. A few businesses, such as taxi and ride-share drivers, must register regardless of revenue.
Because Ontario uses the harmonized sales tax (HST), registering once covers both the federal and provincial portions — you are not managing two separate sales taxes.
It pays to watch your running total rather than checking once a year. The threshold looks at any single quarter and the rolling four-quarter window, so a strong month or two can tip you over sooner than you expect. Keep a simple record of your taxable revenue so you know when you are approaching $30,000 and can register on time instead of scrambling after the fact.
Why register for HST voluntarily?
Even if you are under $30,000, you are allowed to register for HST voluntarily. Many new businesses do, for two main reasons.
First, input tax credits (ITCs). Once registered, you can claim back the HST you pay on business purchases — equipment, software, professional fees, supplies. If you are investing in your business early on, those credits can add up, and a small supplier cannot claim them.
Second, credibility. A registered business charging HST can look more established to corporate clients, some of whom expect to see HST on an invoice. Registering also means you do not have to scramble to sign up the moment you cross the threshold.
The trade-off is real, though: once registered you must charge HST, keep records, and file returns on schedule, even in quarters where you owe little. For a business selling mainly to consumers who cannot claim ITCs, adding HST to your price can also make you slightly less competitive. Weigh the recovered credits against the added admin before you decide.
How the BN relates to incorporation vs. sole proprietorship
How you get your business number depends on your structure.
- If you incorporate (federally or in Ontario), a business number is usually created for your corporation automatically as part of registration, and a corporate income tax (RC) account is often set up at the same time. You then add an HST or payroll account when you need one.
- If you are a sole proprietor, you do not automatically get a BN. You may not need one at all while you are a small supplier with no employees. You register for a BN once you need an HST account, hire staff and need payroll, or start importing and exporting.
In other words, incorporating tends to hand you a BN up front, while a sole proprietor often adds one later — only when a specific program account requires it. If you are still deciding on a structure, our guide on sole proprietorship vs. incorporation in Ontario walks through the trade-offs.
How to register for a business number and HST account
You can register for a BN and its program accounts a few ways:
- Online through the CRA's Business Registration Online service, the fastest option for most people.
- By phone with the CRA's business enquiries line.
- By mail or fax using the appropriate CRA form.
You will need basic information about your business: its legal name and structure, the owners' details, your main business activity, and an estimate of your annual revenue. If you are incorporating, registering the business itself and getting the BN often happen together — see our overview of how to register a business in Ontario for the full sequence.
Once your HST account is open, the CRA assigns you a reporting period — annual, quarterly or monthly, usually based on your revenue — that sets how often you file HST returns. On each return you report the HST you collected, subtract your input tax credits, and remit the difference (or claim a refund). Missing a filing deadline can trigger penalties and interest, so it is worth setting reminders or using a service that tracks the dates for you.
The bottom line
A business number is simply your CRA identifier, and an HST account is one program account on it. You are required to register for HST once you pass the $30,000 small-supplier threshold, and you may choose to register earlier to claim input tax credits. Incorporating usually creates your BN automatically; sole proprietors add one when a program account calls for it.
If sorting out your BN, HST account and other CRA registrations feels like one more thing you do not have time for, that is exactly the kind of setup Markham Office handles day to day. We can register your business number and HST account correctly the first time, so you can get back to running your business — start with our registration service.