Just over 51,000 voters registered for the last election in 2014.
Supervisor of Elections Pita Vuki says the final electoral roll will be printed on September 15.
Mr Vuki told the Matangi Tonga website that he expects the number of voters to be close to that of the provisional roll but there are still voters coming in to register.
The deadline for new voters to register is Thursday.
The provisional electoral roll consists of 51% women and 49% men.
