It has been a while since I have been on an aircraft so I will try to remember this from memory.
I live in Canada. Occasionally when I fly back from USA to Canada, the airline (Air Canada, United Airlines), gives some sort of "sheet" to each of the passengers to fill out before we land.
I am not sure what this sheet is, but it usually asks for your name, where you are travelling, and how much money you spent in the country.
I want to know two things.
Firstly, what is this sheet of paper, and is it always handed out. Is it optional to fill out?
Secondly, why do they need to know how much money we spent in another country. For example in the USA, if I bought a gift (400$), and I am returning to Canada, do I have to pay tax on this?