Leave encashment received

Yes, the entire amount received by the employee pertaining to leave encashment after retiring is exempt.

https://incometaxindia.gov.in/pages/acts/income-tax-act.aspx 

Refer clause 1 of subsection 10AA of section 10 in the above link.

Yes it is exempt from tax.

One of our fellow member filed IT retuns showing it as taxable income. Can we revised ITR if it is within due date?

Yes you can revise ITR.

yes you can revise