Income tax query?

Lalit patidar (Student) (45 Points)

17 July 2016  
My Income tax return for FY 2014-15 is being filed and refund is being credited in my bank account. But later something came to my attention (some amount of TDS being remained unclaimed) which requires revision of Income Tax return. Is it possible to revise the return as Intimation u/s 143(1) is being received and refund already given by Deptt.? Is intimation u/s 143(1) an assessment or not?