CRA indicates that where there is a direct shipment of goods to a customer of a customer, that generally will determine the province of the supply

A supplier, who prepares printed material for a customer (the “Recipient”), delivers the printed matter either by using a Canada Post mail drop, where the printed matter will then be delivered by Canada Post to the Recipient’s customers or proposed customers, or directly to an address (typically a customer’s address) specified by the Recipient. CRA stated:

The CRA’s position has been that where a registered supplier supplies goods on a delivered at destination basis and the terms for the sale of the goods dictate that the supplier must deliver the goods to a destination specified by the recipient, the delivery of the goods will generally be considered to be part of a single supply.

In CRA’s view, it generally would be inappropriate to bifurcate the supply of the goods into a delivery supply and a supply of the goods, and it would generally be necessary to track where each mail drop was being sent in order to determine the provincial place of supply of the goods (the printed material) delivered using the Canada Post mail drop.

Neal Armstrong. Summary of 14 March 2019 Interpretation 152843 under ETA Sched. IX, Pt. II, s. 1.