Treasurer Tom Koutsantonis will reveal a $189 million surplus for 2025/26 when he delivers the South Australian budget on Thursday, up more than $100 million on the figure predicted in December.
There is also increased GST revenue of $225 million, with surpluses across the four-year forward estimates totalling $1.4 billion.
But the opposition insists the budget is ''cooked'' and Labor has no plan to manage the state's debt, which is predicted to balloon to close to $50 billion by 2039.
Mr Koutsantonis said he would deliver a budget that takes necessary action to maintain fiscal restraint while still providing government investment where it is needed most.
The government has announced a partial freeze on recruiting of non-frontline public sector for the next 12 months, which is forecast to cut 1000 positions and save $120 million.
The treasurer described it as "back office efficiency" that would not affect frontline areas such as teachers, police, doctors and nurses.
Flinders University public policy lecturer Josh Sunman told AAP the saving was a significant amount, ''but it's a drop in the ocean compared to what the debt bill is''.
Shadow treasurer Ben Hood said the state needed ''a targeted, attrition-based approach to curb that backroom growth in the public sector''.
''Labor simply has no plan for debt management,'' he said.
''The budget is cooked ... and it is time for the premier and the treasurer to step up to the plate."
Based on mid-year budget review figures from December, debt interest was costing the state more than $5 million a day, or $1.9 billion a year, he said.
''That equates to $61 a second of interest being paid on the debt that South Australians are having to carry for this government,'' he said.
Mr Sunman said the debt burden meant the government had limited budget capacity to respond to the cost-of-living crisis.
''Cost-of-living relief is really reductions in charges, things like stamp duty, and car registration, but with the debt situation, that's not really something this government can do,'' he said.
Much of the increased debt is attributable to the $15.4 billion Torrens to Darlington tunnel project, to complete the city's north-south corridor link, and the new Women's and Children's Hospital, which is costing an estimated $3.2 billion.
The health budget will also top $10 billion for the first time, as the government continues to boost services and staff to address the persistent issue of ambulance ramping.
On Wednesday, Mr Malinauskas confirmed the government's commitment to widen Seniors Card eligibility to all South Australians over 60, as well as Aboriginal South Australians aged 50 or older.
''Currently, if you work 20 hours a week or more, you're ineligible, and that's crazy, because it means that people over the age of 60 are denied ... cost of living (relief),'' he said.
The policy will cost $8 million over four years and allow an estimated 80,000 extra people to access free bus, train and tram travel, and fuel, food and cinema ticket discounts.
Mr Koutsantonis said the Malinauskas government had delivered a surplus in every budget since it was first elected in 2022.
"Ongoing surpluses fortify us against economic shocks and unforeseen spending, and allows us to sustainably manage debt and retain strong economic credentials," he said.
The government will abolish stamp duty on house purchases by victims of domestic, family and sexual violence.
They will also be eligible for the First Home Owner Grant, even if they have bought a home previously, under the scheme designed to help vulnerable women re-establish themselves in secure housing.
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