No, the registration is not possible after the last date of registration i.e. 26 September 2013, even if the Voucher has been purchased on time. Purchasing the voucher is the first step of the registration process and regisration gets completed only after the further steps get finished which includes creation of your profile and hence forth.
Once the Voucher is purchased, is registration possible after the last date of registration?
CAT 2013 is to be conducted by IIM Indore from 16 October to 11 November 2013. Get your questions answered here.