Winston Peters' majority in the Northland byelection increased to 4441 votes, according to the official results.
The preliminary results of the March 28 byelection had his winning margin at 4012 votes.
But since the addition of 1579 special declaration votes and overseas votes, his majority has increase by 429 votes.
Mr Peters, the New Zealand First leader, beat National's Mark Osborne and first-time candidate who polled 11, 648 votes.
Labour's Willow-Jean Prime polled 1380 and will not get her $300 deposit back because she did not get at least five per cent of the votes.
Only Mr Peters and Mr Osborne will get refunds on their deposits.