Arrears of salary are taxable ?

Arrears of salary received are taxable in the P.Y. in which it is received if such arrears of salary paid  to employee in the previous year by an employer or a former employer, if not charged to income-tax for any earlier previous year. However, in other cases as per section 15  any salary due from an employer or a former employer to an assessee in the previous year, whether paid or not is taxable in that P.y. only

Harshal is right that arrears of salary are taxed in the year in which it is received. However, in general, salary is taxable on due or receipt basis, whichever is earlier.

salary is taxable on the basis of receipt or due which ever is earlier. but sometimes arrears are given due to retrospective increase in salary. in such cases it cannot be taxed in the year in the year it belongs to. 

so such arrears are taxed in the year of receipt.

however benifit of releif u/sec. 89 is available.

 

my grandfather is retired principal and receive pension from cg. now, in sept 2015 he is in receipt of arrears of salary when he was in service. it relate back to year 1992 & before. itr was never filed before but started just for last 2 years.
is this amount is taxable now , if yes, how I can take relief u/s 89.
plz note I don't have form 16 for those years