The government have recorded a lower-than-expected surplus, due to a weaker tax take.
Excluding investment gains and losses, the operating surplus stood at $297 million for the ten months to April, compared with the $1.2b gain that had been forecast in May's budget.
Tax revenue came in below expectations at $56.7b, due to a smaller corporate tax haul.
Treasury is putting the discrepancy down to large corporate taxpayers delaying filing their assessments until May or June.
Expenses remained close to expectations, at $60.8m, and if investment gains and losses are included, the operating deficit is a larger than expected at $3.4b.
Net debt totalled $64.4b, or 26.3 percent of gross domestic product.
The Budget forecast growing surpluses and declining debt over the next four years, due to a growing economy and restrained government spending.
