jee main 2021 ki registration date kb s kb tk h

For this year i.e. Jee Main January Session 2020, the application form was released on 3rd September, 2019 and the last date to fill the application was October 10, 2019. And due to this pandemic the situation is not in our hands. So it is really unpredictable when will be the exam as the application has not yet released. As of now there is no Information that the exam of next year will be postponed or not.
It was expected that the application will release in the month of November but it wasn't. Now If the application releases in December 2020, then it will be opened till January 2021. Then it is expected that the first attempt of 2021 will be conducted in February.
On 10th Dec, you can get answer to your query as the Union Education Minister will be taking about the competitive exams. So please till then.
You can start checking the official website, for any kind of updates and if the application releases it will be updated there. There might be a delay in the application of Jee Main 2021 cause most of the events of 2020 have been delayed. http://engineering.careers360.com/articles/jee-main-application-form