The Treasury has warned the Government against making any large spending or tax cut promises as the economy grows faster.
In Budget papers released on Thursday, the department recommends focusing on reducing debt to avoid pushing expected interest rate hikes even higher.
When the Government lifted new spending to $1.5 billion a year In May's Budget, it said that was as high as it could go without triggering higher interest rates.
Treasury papers show the department urged the Government to remain focused on reducing debt to below 20 percent of GDP by 2020 and strengthening the Crown's financial position.
The department said a stronger economy might tempt the Government to spend more and slash taxes, but that might provoke higher interest and exchange rates, and hurt the economy.
Nevertheless, the Treasury argues prudent tax cuts could be possible without damaging the Crown's debt targets.