Voter lists (allowing for on-site registration with ID or proof of address), tear-away serial numbers, and checks throughout the process, including the election official initialing the back of the ballot they hand you and confirming their initials are authentic when you come back with it filled out. In reality you usually don’t go more than a dozen feet from them to mark it anyway. There’s a good rundown here:

http://www.wheresthepaper.org/CountPaperBallots.htm

It helps that it is very rare to have a referendum question so you are usually just voting for your local member of parliament. The ballots are very clear:

http://www.opinionatedbastard.ca/wp-content/uploads/2015/10/...

It doesn’t take that long to count by hand, and it’s rare that people don’t accept a result or engage in conspiracy theories and court battles for months after an election. Recounts happen if the results are very close but there is usually very little movement in totals.

It is apparently a bit more expensive than using machines but I think it’s worth it. There’s something meaningful and beneficial for a civic culture when everyone votes with a tangible physical act in largely the same way it has been done for 150 years. It’s an unusual but radically inclusive act.

Voting by mail is possible by request, but less common, and uses a double envelope system to achieve a similar outcome.

http://www.elections.ca/content.aspx?section=vot&dir=vote&do...