Doubt on Firm Registration Number For CA's

pls help,

My principle is a Individual Practising Chartered Accountant, As per latest notification it is necessary to mention FRN (Firrm registration number) in all audit reports Signed by him.  Is it necesary  to obtain the FRN no for individually practising Chartered Accountant ? if yes can he obtain the number if he want's to continue to practice Individually only ?