Hi Westport676,
Thank you for reaching out to the Microsoft Advertising Community Forum
I can understand your concern about GST/HST business number and will be happy to assist you on this. Just so can I guide you properly, can you please confirm if you are inquiring about Tax information for Microsoft Advertising Account.
I would like to guide you about the process , the VAT/Tax registration number (also called a VAT identification number) identifies a business that has registered to pay VAT directly to your local tax authority, if required. After you enter your VAT registration number, validation can take up to 3 days. You will be notified in Microsoft Advertising if there was a problem validating your VAT registration number. All Microsoft Advertising customers need to have a business location listed for each of their accounts. Business location is the country/region where your business is legally registered. Whether you will be charged VAT on your advertising costs will depend on your business location and your tax registration status. For example, if you are in a business location that has VAT accounting obligations, you will need to enter your VAT registration number. If you do not provide your VAT registration number, Microsoft Advertising will charge VAT, in most cases. VAT will be charged based on your local rate.
Please find below really helpful link for your guidance:
Tax or VAT information (microsoft.com)
I will be sending a private message to you should you need any further assistance.
Thank you,
Farwa | Microsoft Advertising Support Specialist | 800-518-5689