I have always given my SIN because that is what the revenue Canada website says is required and because when I first started daycare the SIN was used by many places as ID rather than a driver's license. That of course has changed and the SIN is no longer acceptable ID in most cases as in they aren't allowed to ask to see it. Another one of those cases where the rules makes no sense since you can't protect something which it says to do on one page if you have to start tossing it around to 10 people a year according to another page.

I do have a disclaimer on my page saying the parent is responsible for keeping number safe or shredding document when no longer needed and that they will be held liable for any damages I suffer due to their negligence. Not going to protect me fully in identity fraud case but at least a start.