Hey Rito

It is not  necessary to take Mathematics in class 12th for doing chartered accountancy course. But it woul be better if you are  good in mathematics level of up to 10th class .

Chartered Accountancy course can be easily done very well by a student who has good understanding of 9/10th class mathematics concept .
First step is to register your self in CPT level of the Chartered Accountancy.
Examinations of the course are conduct twice a year in may and june.
Admission is open through out the year.

hope this helped