When people search for an “HST number” or “GST number,” they're looking for the same thing: the identifier the CRA assigns to your business when you register for GST/HST. Here is what it actually is, when you need one, and exactly how to get it.
This article is for general information only and is not tax advice. Consult a tax professional for guidance specific to your situation.
What an HST number looks like
Your HST number is formally called a GST/HST program account number. It consists of your 9-digit Business Number (BN)followed by the letters “RT” and a 4-digit reference number. A full account number looks like: 123456789 RT 0001.
The 9-digit BN is the core identifier. The RT suffix and 4-digit number identify it specifically as a GST/HST account (as opposed to a payroll account, which uses RP, or a corporate income tax account, which uses RC). On invoices and correspondence you typically see just the 9-digit number followed by RT0001.
When you need one
You are legally required to register for a GST/HST number when your total worldwide taxable revenue exceeds $30,000 in any rolling 12-month period. Once you cross that threshold, you have 29 days to register with the CRA.
“Taxable revenue” means revenue from selling taxable goods or services in Canada. It includes consulting fees, freelance work, design, software development, photography, and most other services. It does not include:
- Employment income (T4 wages)
- Exempt supplies — residential rent, most healthcare services, child care
- Zero-rated exports to clients outside Canada
- Sale of personal capital property
You can also register voluntarily before reaching $30,000. This is worth considering if your clients are businesses — they will claim your HST as an input tax credit and it costs them nothing extra. You also gain the ability to recover the GST/HST you pay on your own business expenses.
What changes once you have an HST number
Registration comes with three new obligations:
- Charge GST/HST on all taxable invoices from your effective registration date forward, at the rate applicable to your client's province.
- Display your registration number on invoices over $30. Clients who are themselves GST/HST-registered need your number to claim input tax credits.
- File returns and remit on your assigned schedule — annual for most small businesses, quarterly for higher revenue.
How to get an HST number
There are three ways to register with the CRA:
- Online:Use the CRA's Business Registration Online (BRO) portal at canada.ca. You receive your Business Number immediately. This is the fastest option.
- By phone: Call CRA Business Enquiries at 1-800-959-5525, Monday to Friday, 9 am to 6 pm local time. Have your SIN, business address, estimated revenue, and intended effective date ready.
- By mail: Complete Form RC1 and mail it to your regional CRA tax centre. Allow several weeks for processing.
For sole proprietors, you will need your Social Insurance Number, legal name, business address, and the effective date you want registration to begin. The effective date should be the day you crossed $30,000 (or the day you want to start, for voluntary registration).
After registration: what to expect
The CRA will mail a confirmation with your account details within a few weeks. Your Business Number is available immediately online or over the phone. From your effective date forward, all taxable invoices must include the applicable GST/HST, and you will begin tracking what you collect versus what you spend on business-related GST/HST (your input tax credits).
The net amount — GST/HST collected minus input tax credits — is what you remit to the CRA at each filing period.
The bottom line
- An HST number is your 9-digit Business Number with the RT0001 suffix
- Required once you exceed $30,000 in rolling 12-month taxable revenue
- You must register within 29 days of crossing the threshold
- Voluntary registration is available and often worthwhile
- Register online at canada.ca for the fastest turnaround
Once you are registered, HST Hero helps you track how much GST/HST you have collected, calculate your net remittance, and stay on top of filing deadlines — so the administrative side of having an HST number stays manageable.