I keep all the receipts until the end of the year then give them all out with a typed page that summarizes every payment with date and amount. That way if the parents send in their receipts or that page to the government they have a duplicate. I'm NOT making up duplicate receipts, that would take too much time so this way nobody loses receipts.

As for your contract question, I make up 2 copies and we all sign both copies so the clients and I each have a legal copy in our possessions.