If my client's head office is in Ontario but the work is used at their branch in Alberta, which tax rate applies?

For most services, the GST/HST place-of-supply rules generally look to the recipient's address that's obtained in the ordinary course of business, most commonly the address most closely connected to the supply, rather than simply defaulting to where the client's head office happens to be located. If the service genuinely relates to the client's Alberta branch, and that connection is properly documented, the supply can be treated as made in Alberta, meaning federal GST at Alberta's rate applies rather than Ontario's 13% HST, even though the client's head office and billing address are in Ontario.

Where a client has addresses in more than one province and it isn't obvious which one the supply relates to, the rules include specific tie-breaking criteria to determine a single applicable province, rather than leaving it to guesswork or defaulting automatically to the billing address. Simply invoicing the Ontario head office without considering where the service was actually used or delivered can lead to charging the wrong rate.

Because these rules can be genuinely intricate once a client operates in multiple provinces, and getting the rate wrong creates real exposure either way, confirm the correct place of supply for each engagement with a tax advisor rather than assuming the invoicing address controls.