According to Section 194-I of the Income Tax Act, 1961, a person who is responsible for paying to a resident any income by way of RENT,
shall deduct income tax (TDS) thereon,
(i) at the time of credit of such income to the account of the payee or
(ii) at the time of payment thereof in cash or by the issue of cheque or draft or by any other mode,
whichever is earlier.
In your case, you have credited the 'rent' to the account of the payee in the Financial year 2015-16, though
you have not made actual payment thereof so far.
As you have credited in your books the rent to the account of the landlord in the year 2015-16 itself, point (i) above is the earliest point, and therefore you are liable to have deducted TDS from such credit and liable to pay to the govt. the TDS amount.