GST/HST Registration

Definition

GST/HST registration is the process of opening a program account (RT0001) under a Business Number so the corporation can legally collect the tax, claim Input Tax Credits, and file returns. Registration is required by ETA s.240 as soon as a person stops being a small supplier, and can also be done voluntarily before that point. A corporation is not permitted to charge GST/HST on invoices until its registration is effective.

Key rules

• Mandatory registration: a person must register when worldwide taxable revenues (self and associates) exceed $30,000 in any single calendar quarter or over four consecutive calendar quarters. See the $30,000 small-supplier rule.
• Effective date: for a threshold exceeded in a single quarter, registration is effective on the day of the supply that pushed the business over. For the rolling four-quarter test, it is effective the first day of the second month after the quarter in which the threshold was crossed, with a one-month transition grace period.
• Taxi and ride-share drivers, non-resident performers, and certain other listed persons must register regardless of revenue level (ETA s.240(1.1)–(1.5)).
• Business Number format: 9 digits + 2 letters + 4 digits, for example 123456789 RT 0001. "RT" identifies the GST/HST program; a payroll account uses RP, corporate tax uses RC.
• How to register: online via CRA's Business Registration Online (BRO), by phone at 1-800-959-5525, or on paper form RC1 "Request for a Business Number". Incorporation provinces (BC, ON) typically push the BN to CRA automatically when the corporation files articles.

Example

A BC corporation is incorporated on March 3, 2026 and exceeds $30,000 in revenue from a single contract invoiced on August 10, 2026. Registration is mandatory immediately.

Registration trigger:  August 10, 2026 (single-quarter rule)
Effective date:        August 10, 2026
Filing with CRA:       Must register before the next taxable invoice
Business Number:       876543210 RT 0001 (assigned by CRA)

First return covers: August 10, 2026 to December 31, 2026
                     (assuming calendar-year reporting period)

The corporation must charge GST/HST on every taxable sale from August 10 forward, even if the CRA account is not yet activated. ITCs can be claimed back to the effective date once the account is open.

Common mistakes

• Waiting for the GST/HST number to arrive before charging tax. The obligation attaches on the effective date, so tax must be collected and remitted even if the number is pending.
• Registering the BN for corporate tax (RC) only and forgetting to add the RT program. The two accounts are separate and must both be opened.
• Using a personal SIN on invoices. The Business Number (BN) plus the RT extension is the registrant identifier, and suppliers must show it for their customers to claim ITCs.
• Backdating registration more than 30 days without CRA approval. Retroactive registration beyond the permitted window usually requires a written request and can be declined.
• Ignoring the non-resident rules. Digital suppliers selling into Canada can have simplified-registration obligations even with no Canadian presence.

Related concepts

Registration is the entry point into the GST/HST system and determines every other obligation. Review the $30,000 threshold to see when registration becomes mandatory, consider voluntary registration if the business is under the threshold but wants ITCs, and use the filing-frequency rules to pick a reporting period at sign-up.