Dear student,

For the year 2021, the JEE Mains exam is going to conduct in the four sessions. You have to fill only one application form for all the four sessions and the Application fee has to be paid depending on the number of sessions you select to appear. Candidates who will miss to apply for February, can apply for March or other session later when the IIT JEE application window will reopen briefly.

For more info, please visit the link given below.

https://www.google.com/amp/s/engineering.careers360.com/articles/jee-main-application-form/amp

Hope it helps.