I want to said that there is no time gap is specified for final registration. You should have a valid final registration number at the time of filing of Final examination form with Institute.
So you take your registration few moths ago before appearing in final exam.
As per Regulation 50 of the CA Regulations, 1988, a student will be eligible to appear in Final Exam, after completing of 30 months (2 Years and 6 months) of article ship.
08 October 2013
If you getting your articleship registration after completion of both groups of IPCC then required to make final registration along with Articleship registration otherwise your articleship registration shall be pending by ICAI for requirement of CA Final Registration.
If doing articleship registration before completion of both groups of IPCC means after completion of first group of IPCC then final registration you shall done after completion of 2nd group of the IPCC but before to applying to the Final exams(submission of Final examination form).