Rent received.

Agreement mean contract.The rent Agreement is contract and hence Indian contract Act  will be applicable.As per the Indian contract Act  a Contract can be in written form or Oral form. So it is not required that a contract should be in written form. Secondly,So far as India Income Tax Act  is concerned the main thing which is to be considered for the Income tax is Income,Source of Income ,place from which the income is generated . In my view there no anywhere is written that there should be written agreement or contract .However it is always advisable that any contract or agreement should be in written form.