The domestic part of a continuous outbound international freight movement is zero-rated and you do not charge GST/HST if the following conditions are met:
The domestic freight transportation services are zero-rated only if they are part of a continuous outbound freight movement. One of the requirements is that the goods transported cannot be processed, transformed, or altered in Canada after the shipper transfers possession of the goods to a carrier and before they are exported, except to the extent necessary to transport the goods. This might include packing or refrigeration to make sure that the goods arrive at their destination in good condition. Domestic freight transportation services used to move raw materials to a processing plant, such as grain moved to a dockside elevator to be cleaned, dried, and graded before being exported, are subject to GST/HST, unless interlining applies.
For more information, see Booklet RC4080, GST/HST Information for Freight Carriers.