from when online application will start for MBA?

Dhruvi, There are quite a few Entrance examinations for MBA in India. Few of them are:

CAT: CAT is an online examination of 3 hours duration. To be eligible for CAT, you should have completed your Bachelor's degree in any discipline with a minimum aggregate of 50%. It is 50% for General Category and 45% for Reserved Categories.

MAT: To be eligible for MAT, you should have completed your Bachelor's degree in any discipline. There is no minimum aggregate criteria.

IIFT: To be eligible for IIFT, you should have completed your Bachelor's degree in any discipline with a minimum aggregate of 50%. It is 50% for General Category and 45% for Reserved Categories.

SNAP: To be eligible for SNAP, you should have completed your Bachelor's degree in any discipline with a minimum aggregate of 50%. It is 50% for General Category and 45% for Reserved Categories.

NMAT: To be eligible for NMAT, you should have completed your Bachelor's degree in any discipline with a minimum aggregate of 50%. Candidates with a minimum of 2 years work experience are preferred.

CMAT: To be eligible for CMAT, you should have completed your Bachelor's degree in any discipline. There is no minimum aggregate criteria.

You can check the complete list at our page: https://bschool.careers360.com/articles/top-mba-entrance-exams-you-must-take

At this point in time CAT registrations are going on. CAT is the entrance examination for admission to all the 20 IIMs and as many as 1000 participating Institutions. You can fill in the registration form for  CAT at: https://cdn.digialm.com/EForms/configuredHtml/756/66504/Registration.html . But if you are enquiring about any other exam for MBA please do help us with that and we shall help you with relevant information.