The net debt of the NSW "general government sector" stood at $5.5 billion at the beginning of the last financial year but had been eliminated by June 30, 2016, a financial report released on Thursday says.

In a statement Ms Berejiklian announced the government has "wiped out the state's net debt".

The state budget in June said net debt had been reduced last year by the proceeds from the recent $10.3 billion privatisation of TransGrid, the state's high-voltage transmission network.

But the budget also forecast general government sector net debt – the metric Ms Berejiklian says is now in the black – to reach almost $25 billion by 2020. Even the big privatisations the Baird government still has in the pipeline might not be enough to offset that increase.

The budget papers also show the broader measure of "total government sector" net debt – which includes the liabilities of state-owned businesses such as utilities – stood at $39 billion on June 30 and is forecast to rise to $69 billion by 2020.

Last week the international ratings agency S&P Global Ratings described the NSW government's debt burden as "moderate".

The S&P report said financial management in NSW was "strong" and confirmed the state's triple-A credit rating. However, S&P's ratings outlook for NSW was automatically downgraded in July because the ratings outlook for the Commonwealth government was downgraded.

S&P said the negative outlook for NSW "reflects that on the Commonwealth of Australia ... we do not consider that any state or territory in Australia, including NSW, can maintain stronger credit characteristics than the sovereign in a stress scenario".

The annual Total State Sector Accounts report, released by Ms Berejiklian on Thursday, shows a final NSW budget surplus of $4.7 billion in 2015-16 – $1.3 billion more than forecast in the June budget.

The improved surplus was due largely to one-off items including higher realised distributions from investments and actuarial valuations in SICorp.

Ms Berejiklian said NSW was leading the nation in economic and fiscal management.

"Our fiscal discipline and asset-recycling strategy has allowed us to invest record amounts on infrastructure while securing our triple-A credit rating," she said.

"This unprecedented infrastructure program is also supporting our booming jobs market, solid housing construction industry and helping to boost consumer confidence and business investment."