The government's finances are in better shape than expected because of a stronger tax take.
The official accounts for the six months ended December show a budget surplus of nearly $1.1 billion, more than three times what was forecast.
Treasury said personal and sales tax returns were about $600 million higher than expected, and expenses were marginally lower.
It expected the tax take at the end of the year to stay ahead of forecast, it said.
The net debt level was also slightly lower than expected at $64.5 billion.