A few months back I've purchased a set of expensive headphones in the US and dutifully declared them when coming back to Canada. Now I would like to travel to the US again and carry the same headphones in my backpack. When coming back to Canada, would I need to re-declare the item as technically it wasn't purchased in Canada? If not, how do I prove that the headphones have already been imported to Canada and I don't need to pay duty on them any longer?
If it matters, in the first trip I've verbally declared that I'm carrying the headphones when re-entering Canada by car and thus didn't have to fill out a customs declaration. I did not pay any duty as I was below the duty free limit at that time.