Collect all Payslips
Make sure to collect all the salary slips. In case, you have switched jobs one or more times in the same financial year, make sure to gather all payslips of the assessment year from all the previous jobs.
From this year on, the government has made it mandatory to fill in complete breakup of your salary in your ITR.
The fields required to be filled are - salary/pension, allowances not exempt, value of perquisites, profit in lieu of salary, and deductions claimed under Section 16. Your salary slips should normally provide these figures.