CLAT is the National Level Exam for the admission to Undergraduate law programmes including BA LLB, BBA LLB, BCom LLB and BSc LLB into National Law Universities. As per the eligibility you should have minimum 45% in 10+2 as a General Category & 40% as a reserved category. The Online registration is exepcted to start from 1st January, 2019. You can check the complete detail about the exam with the give below link.

https://law.careers360.com/articles/clat-application-form

If you are asking about any particular B.A LLB exam then mention the exam name.

Good Luck!