hello aspirant,

firstly, i will tell you the basic eligibility for b.com 

1)you should have completed 10+2 exam and must pursue 50% to 60% in his academics. 

2)admission is purely based on merit 

merit list is determined on the basis of 12th marks.cutoff's are anounced by universities and colleges when after the student reached the range of marks in exam 

also, there is no entrance exam conducted centrally for b.com admissions 

some of the universities conduct entrance exam on a university level such as BHU. 

to summarize, you should be getting 50 percent to 60 percent range / above in your 12th to get admission for b.com 

thank you