Look at it like this.

When there is a reassessment in your favour, it works the same way. You get your money back, plus interest. Happened to me.... CRA did a reassessment on a previous tax return years after the fact, and it turned out to be a welcome surprise.

Works both ways.

The onus is on you to properly and correctly report your income. If you can't manage that yourself, then you should hire someone you trust who can do it for you on your behalf.