You will get back your security money after completion of all rounds of counseling.
But there are few conditions like :
1.if you are alloted a college in the 1st round and you report in the college or whether you don’t report it never matters you have a chance of free exit.
2. Now if you take part in the 2nd round and you are alloted a college then there is no free exit policy you have to report to the college or if you don’t want to take the alloted college then the money you have deposited will not be refunded.
In case you took admission in the alloted college your money will be refunded.
3. If you were not alloted any college in the 1st round and you did not participated in the 2nd round then also your money will be refunded.
If you are still not clear you can go to the official website of nta and read the faq section for further details.