18 December 2013
Like IPCC there is no pre-registration period for CA Final registration. So you can register it at any time but before to applying(submission of exam form) to exam for your attempt.
Note: In case if you registering to CA Articleship after completion of both groups of IPCC then CA Final registration also required to complete along with articleship registration, otherwise ICAI shall keeping your articleship registration pending upto getting final registration.
Generally the time period is not specified for final registration. You should have a valid final registration number at the time of filing of Final examination form with Institute.
So I will suggest you to take registration in final 3 months before filing the examination form. At that time the Institute will send your final registration letter.
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.