income from rent...

Rahulsgupta (40 Points)

10 May 2007  
an assessee used to file his return of income showing income of rent on recipt basis and was assessed accordingly upto the assesment year 2005-06. during the financial year 2005-06, he recieved a sum of Rs 50000 by way of enhancement for the last six years as the government department(tenant) enhanced the rate of rent with retrospective effect. will the sum of Rs 50000 be taxable in the assesment year 2006-07? can it be spread over the last six years? is there any provision of tax relief in such cases?
    
plz help me out??????????/