From the Canada Revenue Website when searching for GST/HST account numbers.

GST/HST account number

Enter only the first nine digits of the GST/HST account number. Do not include letters.

A supplier must include the GST/HST account number on receipts, invoices, contracts, or other business papers it gives out when it supplies taxable goods or services of $30 or more.

If you can't find the GST/HST account number, contact your supplier. When your supplier does not provide their GST/HST account number, call the Canada Revenue Agency's Business enquiries line at [phone number removed] to confirm it is registered.