The complete procedure of all india counselling is as follows:

1. Online registration, fee payment, submission of form, choice filling an locking of choices
2. This is followed by the 1st round of seat allotment
3. If you are allotted with a seat, you have to report to your institute and complete the formalities there. If unfortunately you do not get the seat, you can apply for round 2 (candidates already registered for round 1 need not pay the fee.). Fresh candidates can register for round 2 again and pay the fees.
4. Even if you have been allotted a seat in round 1 but wish to upgrade, you can participate in the 2nd round (candidates satisfied with their seats need not do so).
5. Choices filled in round 1 will not be valid, so you have to fill the choices again. This is mandatory for all candidates.
6. Second round of seat allottment takes place. The candidates who have successfully secured their seat in round 1 and 2 get the refund of registration fee.
7. If you still do not get a seat after the 3rd round, you can re apply for the mop up round similarly.

Candidates obtaining a seat in the second round are not allowed to vacate the seat what so ever.