suppose u are getting a rent of 10000 p.m nd u demand a rent of 20000 pm nd ur tenant is not ready to pay it..u get into a dispute nd after 5 yrs u win the dispute nd get rent as 20000 pm for past 5 yrs...this difference of 10000 p.m u will recieve as arrears of rent nd will be taxable in the year in which it is recieved u/s 25 B....deduction u/s 24 A can be claimed as well.....
unrealised rent received will be taxable u/s 25 AA.....if it fulfilled the conditions at the time it was unrealised....i.e the tenant must have left,tenancy must be bonafide.,he shoud not have occupied any other house of the assessee nd all procedure regarding collection of rent have been fulfilled,......