Whenever you take rent in the form of cash, you should give a rent receipt. If you fill it out in duplicate then you each have a record of what was paid.
This particular receipt also gives two statements: that the payment is for use and occupancy only, and that all rent owed prior to this date has been paid in full. You may wish to strike out one or the other. The "use and occupancy" line comes into play if you take a partial payment. You're not waiving your right to the full contractual rent. The "paid in full line" applies if it's true. We added it so that a tenant need never ask for a separate letter confirming rent has been paid.
Rent receipts also protect you if you end up in eviction proceedings and/or discovery. If you can easily show a record of past receipts for cash payments, you will lend credibility to your assertion that rent has not been paid, even if the tenant says it has.