The answer is: You'll have to pay interest if your owe something and nothing if you're owed something.
My friend used to wait until I was tired of reminding him and I would do it for him (usually around October) and it's never been an issue with the CRA.
Seriously this Canada group is exactly like the Reddit Canada group.. everybody sucks Trudeau's asshole here... I've never been downvoted more than in my own fucking country's groups.