You would be foolish not to ask for a receipt for each payment that you make to your landlord, as this is the proof that you are up to date with your rent payments. If your landlord will not provide you with a receipt, then you could purchase your own receipt book from any stationery shop and complete the transaction yourself, and just get your landlord to sign it each week or month.
Nowadays though, you should think of other ways to make your cash payment as paying rent this way is asking for trouble. Unlike paying by cheque or direct debit there is no traceable way of tracking your rent payments.
If you have no choice but to pay your rent in cash then follow these precautions to avoid putting yourself at risk:
1) Always hand your cash to someone of authority, such as the landlord himself or the letting agent who is handling the tenancy agreement.
2) Never send cash payments through the post. The postal system is not always reliable and items often get lost in the post, not to mention if it gets into the hands of an untrustworthy member of staff.
3) Don't leave without a receipt. If your landlord refuses then you should be suspicious about the transaction.
4) Always keep your receipts in a safe place at home. A good idea would be to keep your lease agreement and the receipts in the same place.
The easiest way is to set up a direct debit to your landlord. This will ensure that the payment is made automatically every month, and the transaction is shown on your bank statements.