The days of government budgets concentrating on longer-term issues are over, a new analysis from Deloitte Access Economics suggests.
The relationship between Treasury and the Reserve Bank of Australia went through an important shift during the COVID-19 pandemic.
The Reserve Bank is the instrument to handle the ups and downs of the economy by raising or lowering interests rates.
But with interest rates on the floor, Deloitte's leading economist Chris Richardson says "budget policy has to be more agile than it's been in times past".
"That means a greater willingness not merely to use the budget that way, but also an understanding from both the public and the opposition of the day that any such policy moves - such as tax surcharges and discounts and spending shifts - are temporary," he said.
The Deloitte analysis follows the federal budget in October, and forecasts that the Treasury has underestimated the size of the economy.
China's trade war may have hurt Australian businesses and Chinese families, but it has been an awkward win for Australia's budget outlook, the analysis suggests.
Iron ore prices have shot up to levels not seen since 2013. Mr Richardson says the "fear tax" surrounding China's mystery bans and sabre-rattling is driving up prices, along with other factors, in ways that the government's budget just two months ago did not predict.
"The bottom line is that China's trade war with Australia is making us money rather than losing it," Mr Richardson says.
"To be clear, we've lost money on everything from lobsters to wine. But we've more than made that up in overall terms thanks to iron ore - and the taxman will be a considerable beneficiary of that."
Deloitte's forecasts the economy will be $33 billion larger than Treasury itself projected, a gap that will increase over time to $106 billion by 2023-24.
The bigger the economy, the more people in jobs paying taxes, and higher than expected profits mean more wiggle room for Treasury as it tries to shave off the projected deficits in coming years.
Eyes have been watching Australia's AAA credit rating after NSW and Victoria were downgraded to AA+ and AA respectively, but Mr Richardson says a downgrade wouldn't necessarily hurt Australia.