"The Government's books are in good shape, as evidenced by last week's release of the monthly accounts. We are running surpluses so that we have money aside for a rainy day, and we are cutting net debt to 20 per cent of GDP within five years of taking office," Robertson said.
The Budget Responsibility Rules mean that government expenses and revenue as a proportion of the economy remain stable, and both are below 30 per cent of GDP.
"At the same time, the Coalition Government is making record investments in New Zealand's infrastructure. This includes the highest amount of capital investment for hospitals in at least 10 years - $850 million in Budget 2018," Robertson said in a statement.
Treasury released its financial statements for the 11 months to May 31 last week.
Core Crown tax revenue of $73.49b was in line with forecast. Core Crown expenses of $73.02b came in $439 million (0.6 per cent) below forecast.
The operating balance before gains and losses was a surplus of $5.228 billion in the 11 months to May –$447 million, or 9.3 per cent above the Budget forecast.
Debt was at 20.1 per cent of GDP, below the forecast of 20.4 per cent, but still close to the Government's target of 20 per cent. Core Crown net debt at the end of May was $1.8 billion lower than a year ago.