Rent relating to the Period 1/12/10 to 31/03/11 is taxable under the head "Income from House Property"
However you should remember tht if the HP is let out for part of the year the entire year's Rent will be chargeble to tax. And yes offcourse you could claim Vacancy Period Rent Deduction if you satisfy the provisions of Sec 23(1)(C).
Thank you,
Regards CA. Lohith.J B.Com,ACA,CS,(ICWA),SAPM Hons,ITF Hons