The government books recorded a $934 million surplus, before investment gains and losses, in the seven months to the end of January.
That was $724m higher than forecast, mainly due to a higher than expected tax take, and lower Crown expenses.
Tax revenue from GST and income tax was $200m more than forecast, and the main reason the surplus was higher than initially estimated.
The Crown's expenses were also lower.
Treaty settlements cost $177m less than expected because of ongoing negotiations, and spending from the Inland Revenue Department and the education sector was lower than predicted.
Finance Minister Bill English said the higher surplus reflected ongoing careful financial management, but also showed volatility in the monthly accounts.
He said the government wasn't reading too much into the latest financial statements, and would continue to keep a tight lid on spending.