One of the ways a registered political party can be recognised as a national party - If it is recognised in at least 4 states as a state party.
Legislative Department, Government of India
For any political party to be eligible for recognition as a national party, it has to satisfy any of the three conditions as per the criteria listed in ‘The Election Symbols (Reservation and Allotment) Order, 1968’. This order is amended from time to time.