Regarding Perquisite Tax on ESOP - Unlisted Company

Dear Experts,

I have one query regarding Perquisite Tax on ESOP for Unlisted Company ( Holding Company -USA Inc .  ) . Stock options of USA company is granted to Indian employees . In case the employee quits the company and later on exercise his ESOP option . As an Employer-Subsidiary Company , how to deal with ensuring Perquisite tax recovery against this exercise of ESOP. 

Any Notification or Cirlular from Govt on this matter is very helpful.

Thank You