The best way to pay a rent is by traceable payment methods: bank transfer or check.
In this case, a payment receipt is not needed.
If you wish to pay your monthly rent in cash, remember that the cash transfer for the current year can’t exceed the amount of 2,000 euros.
The capex implies that all cash payments exceeding 2,000 euros have to undergone the anti-money laundering registration (registrazione anti-riciclaggio).
If you rent through an agency, it has the duty to inform you on this registration.
For all the cash payments it is highly advisable to ask for a receipt of payment. The release of the payment receipt is not mandatory, but if the tenant requires it, then the landlord is obliged to give it.
PS: on every receipt there should be put a 2 Euros duty stamp if the amount exceeds 77.47 Euros.