Hello Nikhil. 

The Applications for CBSE Improvement Exam 2019 will be made available in September or October 2019 on the official CBSE website.

Improvement Exam 2019 is only for those candidates who want to raise their previously scored marks in Board Exam.

Candidates can apply for Improvement Exam 2019 for all the five subjects or for the selected subjects from the five main subjects..

Hope this will help you.!!

Good luck.