Interest income tax liability

Hello, One of my relative deposited Rs.5 Lakhs in a Financial Institution. The Scheme is as folows - Within 5 and a half year the initial deposit ie. Rs.5 Lakhs get doubled.The amount accrued and credited Rs. 10Lakhs in his bank account during 2015-16. During these years no Tds deducted . How he file his income tax return during the F.Y 2015-16? What is the tax treatment of Rs. 5 Lakhs (interest income) received? Can we consider Rs.5 Lakhs as income of F.Y 2015-16 and compute income tax by applying slab rate in the head " Income from Other Source"? Can he take Chapter VI Deductions? Waiting for your advice.