GST/HST number on an invoice: when you need it and where it goes

A GST/HST number belongs on every invoice of $100 or more. It is the 15-character registration number — nine digits, the letters RT, four more digits — and the regulation that requires it is aimed at your customer, not at you: without the number, the general contractor or property manager you invoiced cannot claim the input tax credit. In Quebec the QST number goes next to it.

So the number is less a formality than a payment condition. An accounts payable clerk who cannot claim the credit on your invoice sends it back, and the 28 days you were counting on start again.

The number, character by character

The CRA's registrant guide RC4022 describes it plainly: "When you register, you will have a 15-digit registration number. The 9-digit BN identifies the business followed by 2 letters which identifies the program (RT is for the GST/HST program) and a 4 digit number which identifies the specific account, for example: 123456789 RT 0001."

Two mistakes come from that structure:

• Printing the business number alone. The nine digits identify your business across every CRA program — GST/HST, payroll deductions, corporation income tax. Only the RT account is the GST/HST registration. "BN 123456789" on an invoice is not the number the regulation asks for.
• Printing the payroll account by accident. A business with employees also has an RP account under the same nine digits — the CRA's own example is 123456789 RP 0001. Copying the wrong line from a CRA letter puts 123456789 RP 0001 on every invoice, and it will not match anything on the customer's side.

The $100 line, and what each tier adds

The Input Tax Credit Information (GST/HST) Regulations set three tiers, measured on the total of the document. The thresholds were raised by S.C. 2024, c. 15, s. 142; a great deal of guidance still prints the old $30 and $150.

Almost every construction invoice lands in the third row, which is why the full list is in invoicing for contractors: the $500 tier and holdback. This article is about the one field that decides the credit.

Separately from the credit rules, section 223(1) of the Excise Tax Act requires any registrant making a taxable supply to show either the consideration and the tax "in a manner that clearly indicates the amount of the tax", or that the amount includes the tax. The number tells the customer who charged the tax; section 223 makes sure they can see how much.

Quebec: two numbers, two taxes

On work in Quebec, GST and QST are separate taxes with separate registrations: the GST/HST number comes from the CRA, the QST registration from Revenu Québec. Since January 1, 2013, the QST has been charged at 9.975 percent on the price before GST, which is why the two add up to 14.975 percent (Finances Québec, Information Bulletin 2012-4). The QST follows Quebec's own legislation, not the federal regulations above, so its invoicing rules are Revenu Québec's to state.

The RBQ number on a Quebec invoice is a construction rule, not a tax rule: RBQ licence verification: who needs one, and how to check it.

A sample: where the numbers go

A plumbing company in Toronto invoices a condominium corporation for a bathroom renovation in common areas. Total $4,364.96, so the third tier applies.

The number sits with the supplier's details or in the footer, consistently on every page — there is no prescribed spot, only a prescribed presence.

Small supplier: no number, and no tax on the invoice

If your taxable supplies did not exceed $30,000 over the four preceding calendar quarters, you are a small supplier (Excise Tax Act s. 148) and registration is not required (s. 240(1)(a)). That has two consequences on the document:

1. No GST/HST number, because there is none. Do not print your business number in its place — it suggests a registration that does not exist.
2. No GST/HST charged. The invoice shows the price, and your customer has no input tax credit to claim on it.

The test runs quarter by quarter, so the day a large job pushes you over is the day to look at registration again — when tax becomes payable on progress billings and holdback is in GST/HST on holdback: no tax before the holdback is payable.

How your customer checks it — and why that matters to you

The CRA runs a public GST/HST Registry for exactly this. The customer enters the first nine digits of your number, without letters, your business name as it appears on the invoice, and the transaction date. The CRA's own instruction is to "Print the Search Details screen to make sure you claim input tax credits only for GST/HST charged by suppliers who are registered."

Two practical consequences:

• The name has to match. A trade name on the invoice that the CRA does not know under your registration makes the search fail. If you trade under a different name than your legal one, put both on the letterhead.
• A wrong digit is caught by the customer, not by you. Before the first invoice of a new year or a new template, run your own number through the Registry once.

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Position as at October 4, 2026, checked against SOR/91-45 as current to September 21, 2026, sections 148, 223 and 240 of the Excise Tax Act and the CRA's RC4022, program account and Registry pages. What may change: the dollar tiers are set by regulation and were last moved in 2024; a further change would come through a budget implementation act, so check the "current to" date on the Justice Laws page before relying on $100 and $500.

What Zirko does here: the GST/HST number is a field of its own in the company settings, and Zirko will not finalize an invoice of $100 or more from a registered business without it — the check runs on the server, not in the browser. The number then prints in the footer of every document. A QST number is printed when you enter one; Zirko does not refuse an invoice without it. Zirko does not look your number up in the CRA Registry and does not decide whether you are a small supplier — that follows from your own four quarters. How the invoice is built from the quote, holdback included, is on job documents.