How to Find Your GST Number

July 31, 2026 Lord AI Editorial Team

A Canadian GST/HST number is not usually a standalone random identifier. It is a program account attached to the CRA business number and commonly includes the letters RT plus a four-digit reference.

Use official records to distinguish your own account from a supplier’s number and from other federal or provincial program accounts.

Quick Answer

Check the original CRA registration confirmation, your CRA business account, recent GST/HST returns and notices, and verified invoice templates. If the number cannot be confirmed, contact CRA business enquiries before filing or charging tax.

Know Which Number You Need

In Canada, a GST/HST account is part of a business number issued by the Canada Revenue Agency. The account commonly appears as a nine-digit business number followed by the program identifier RT and a four-digit reference number, such as 123456789 RT 0001.

Do not confuse a GST/HST account with a provincial sales tax number, Quebec sales tax number, payroll account, corporation number, or import-export account.

Check Your CRA Registration Documents

Look for the CRA confirmation letter or electronic registration confirmation issued when the GST/HST account was opened. It should identify the legal business name, business number, program account, effective date, and filing frequency.

Use the legal entity’s records. A sole proprietor, corporation, partnership, and newly reorganized business may have different accounts.

Use CRA Online Services

Sign in through the appropriate CRA business service and review program accounts associated with the business number. Ensure the person signing in has the required authorization for the business.

If the business has recently linked or changed an account, allow processing time and verify that the GST/HST program account is active rather than relying only on an old invoice.

Review Returns, Notices, and Payment Records

A previously filed GST/HST return, notice of assessment, statement, remittance voucher, or CRA correspondence generally shows the program account. Accounting software and prior-year workpapers may also contain it.

Compare the name and address to current records. Using the number of a predecessor, related company, or previous owner can misdirect returns and payments.

Check Invoices and Contracts Carefully

If the business is registered, its GST/HST number may appear on sales invoices, receipts, contracts, online checkout settings, or tax configuration pages. Treat these as leads, not final proof, because templates can contain outdated data.

Never copy another supplier’s number or use a number found online for your own business.

Contact the CRA When You Cannot Locate It

Use the official CRA business enquiries channel. Be prepared to verify identity and authority using the legal business name, address, ownership details, business number information, and recent filing records.

Do not send sensitive account numbers through ordinary email or social media.

Verify a Supplier’s Registration

When you need to confirm that a supplier’s GST/HST account is valid for input tax credit documentation, use the CRA’s official GST/HST registry or verification process. Enter the supplier’s legal or operating name and the account details exactly as requested.

A valid number does not by itself prove that every charge is correct; the invoice must also meet documentation requirements.

What to Do If the Number Is Missing or Inactive

Determine whether the business was required to register, registered voluntarily, changed legal structure, closed the account, or received a new business number. Do not collect GST/HST under an inactive or nonexistent account.

Correct invoices, returns, and payments promptly after confirming the proper account. Obtain professional advice where registration dates, unreported tax, input tax credits, or business reorganizations are involved.

Writer’s Opinion

The most common risk is not that a business cannot find any number; it is that someone finds an old or related entity’s number and assumes it is correct. I would match the legal name, business number, RT account, effective date, and current registration status before using it.

For bookkeeping, store the verified account in a controlled tax-profile record rather than relying on invoices or memory. Restrict who can change tax identifiers in accounting and ecommerce systems.

Frequently Asked Questions

What does a Canadian GST/HST number look like?

It generally contains a nine-digit business number, the program code RT, and a four-digit reference number, often displayed as 123456789 RT 0001.

Is a business number the same as a GST number?

The nine-digit business number identifies the business in CRA systems. The GST/HST account adds the RT program code and reference number.

Can I look up another company’s GST number?

The CRA provides an official registry or verification service for checking a supplier’s GST/HST registration using required business information.

What if I changed from a sole proprietorship to a corporation?

A new legal entity may require a different business number and GST/HST account. Confirm the effective dates and do not continue using the predecessor’s account automatically.