How to pay income tax on arrears

Hi,

I have a client who got Arrears form  in April-2017 without paying Income tax, but he has not filed any income tax return till A.Y.15-16, and A.Y.16-17 filled without claiming Arrears of that year, 

My question is, can he claim part of the arrears which was due in the year of F.Y.16-17 and received and April-2017,

Regards

CA  Hakim