I've used 2 different accountants (one was a hdcp herself) and both said it's fine to only give it if requested if a parent gets audited. I just tell all my clients to give my contact info to their accountants and if they want it, they can call me and I'll give it than

For security reasons, I don't like my SIN to be on their receipts in case it gets lost/misplaced. My current accountant said that is reasonable