Section 89(1)

Do one thing ,
i) calculate tax on the amount ( arrears received(total) + salary of the p.y).
ii) calculate tax on the amount of salary in the p.y.

iii) calculate tax on the amount of the individual years (salaries (arrears accrued to that year + salary of that year).
iv) calculate tax on the income of the individual years(without considering arrears).

Rebate = ( i-ii) - (iii-iv).

Tax is calculated after taking all the deductions available for that year.

I hope you understand.

Thanks sir