When You Must Register for HST/GST in Ontario: A Small-Business Guide

Many Ontario small-business owners and freelancers are surprised to discover that income tax is not their only CRA obligation. Once your revenue crosses a certain threshold, you are legally required to register for, collect, and remit the Harmonized Sales Tax (HST) — or, for businesses operating in provinces with separate federal/provincial systems, the Goods and Services Tax (GST). In Ontario, HST applies at a combined federal-provincial rate.

Failing to register on time, or failing to remit what you collect, can lead to CRA penalties and interest. This article explains the trigger, the timeline, what to do when you register, and a few nuances worth knowing. Confirm all current rates and thresholds with the CRA or an accountant — they are subject to change.

The Small-Supplier Threshold

The CRA classifies businesses with taxable supplies of goods or services below a prescribed annual amount as small suppliers, which exempts them from mandatory HST/GST registration. As of writing, this threshold is $30,000 in total taxable revenues in any single calendar quarter or over four consecutive calendar quarters — verify the current threshold with the CRA before relying on this figure.

Once you exceed the threshold — whether in a single quarter or cumulatively over four quarters — your status as a small supplier ends and your obligation to register begins.

The Registration Timeline

The moment you cease to be a small supplier, you generally must register for HST/GST before the end of the month following the quarter in which you exceeded the threshold. The CRA's rules on timing are specific and fact-dependent; confirm the exact deadline for your situation.

Importantly, once you exceed the threshold, you are required to begin collecting HST on your taxable supplies — even if you haven't formally registered yet. Retroactive registration is possible, but it creates administrative headaches. Monitoring your revenue and registering proactively (or before you expect to exceed the threshold) is cleaner.

Voluntary Early Registration

You can register voluntarily before reaching the threshold. Many businesses do this to claim Input Tax Credits (ITCs) — the mechanism that lets you recover the HST you paid on your own business inputs (software, supplies, services). If you are spending significant amounts on HST-bearing expenses, early registration may save you money even at low revenue levels.

What Is a "Taxable Supply"?

Not everything you sell is a taxable supply. The Excise Tax Act places supplies into categories:

• Taxable supplies (including zero-rated): standard goods and services, professional services, most consulting, trades work, retail sales
• Zero-rated supplies: goods and services taxed at 0% — certain basic groceries, prescription drugs, some medical devices, exports
• Exempt supplies: financial services, residential rent, most health services, educational services from specified institutions — HST does not apply and no ITC may be claimed on related expenses

If your revenue is primarily from exempt supplies (for example, a residential landlord), you may never hit the registration threshold in a meaningful way. If you provide a mix, the analysis can be more complex.

How to Register

You register for an HST/GST account through the CRA:

• Online via CRA My Business Account or BizApp
• By phone to CRA business enquiries
• By mail using form RC1

Upon registration, the CRA assigns you a Business Number (BN) with an "RT" suffix identifying your HST/GST account. Your invoices must include your Business Number and the amount of HST charged once you are registered.

Filing Periods and Remittance

Once registered, you file HST/GST returns on a schedule assigned by the CRA — monthly, quarterly, or annually, depending on your annual revenue. The return reports:

• HST collected from customers
• Minus ITCs (HST you paid on business expenses)
• Net amount owing or refund due

Keeping careful records of HST collected and ITCs claimed is essential. Mixing HST money with your operating funds is a common mistake — many business owners keep a separate account or set aside the HST portion of every invoice payment.

Input Tax Credits: The Other Side of the Ledger

One significant benefit of HST registration is that you can recover the HST embedded in your business expenses through ITCs. If you pay $130 for a $115 + $15 HST supply, once registered you can claim that $15 back against your HST remittance. For businesses with substantial input costs, ITCs can meaningfully reduce the net HST payable.

What Happens If You Don't Register on Time?

The CRA can register you retroactively and hold you liable for HST that should have been collected and remitted, even if you never collected it from your clients. Penalties and interest apply. In practice, this means you could owe HST out of your own pocket for periods where you were invoicing without it.

Special Situations

• Incorporated businesses have the same threshold obligation — the threshold applies to the corporation, not the individual.
• Non-resident businesses selling to Canadian consumers may have separate HST obligations under the digital services rules.
• Ride-share and delivery-platform drivers are subject to specific rules that may require registration regardless of revenue — confirm with the CRA.

Frequently asked questions