As its stands, economists expect the deficit could balloon to as much as $240 billion for the 2020/21 financial year after Treasurer Josh Frydenberg hands down his second budget on Tuesday night.

It is a far cry from the $6.1 billion surplus predicted last December - before the COVID-19 pandemic set in and the economy reeled into its first recession since the early 1990s.

In a change of fiscal strategy, the government will no longer be pursuing surpluses until the unemployment rate is comfortably below six per cent.

Instead, the government is promising to spend to create jobs, encourage investment and stimulate the economy, as seen in a stream of pre-budget announcements.

Billions of dollars have already been promised for small business, infrastructure, energy, the digital economy, apprenticeships, tourism and the regions.

How quickly these measures will assist getting people back into work remains to be seen.

Mr Frydenberg notes that after the 1980s recession it took six years to get the unemployment rate back below six per cent and 10 years after the 1990s recession.

"Unemployment tends to go up the elevator and come down the stairs," he told ABC television.

"We are hoping to move faster than that and that is why in this budget you'll see more economic activity as a result of our initiatives, creating more jobs."

As such, shadow treasurer Jim Chalmers says if the government doesn't prevent unemployment being too high for too long, "then it will have failed".

The jobless rate unexpectedly fell to 6.8 per cent in August from 7.5 per cent, but both the Reserve Bank and Treasury expect it will resume its rise having previously predicted a peak of around nine per cent.

"We do not expect the government to forecast an unemployment rate below six per cent until 2022/23," Commonwealth Bank head of Australian economics Gareth Aird says..

Westpac economists are expecting the budget forecasts to be more pessimistic, with the unemployment rate still at 6.5 per cent as far out as 2023/24.

In that environment, wages growth will likely remain sluggish and the government will need to maintain support for the jobs market, they say.

With so many initiatives already announced and so much money already promised, it is difficult to know what there will be left for the treasurer to reveal at the dispatch box on Tuesday night.

However, the government has repeatedly flagged it will bring forward already legislated personal income tax cuts due in 2022/23 to help stimulate spending. There is speculation these could be backdated to July 1.

There has been plenty of debate as to whether these would have the desired impact as they benefit higher income earners, who are more likely to save than spend.

Even economists such as Mr Frydenberg's former employer Deutsche Bank don't believe this is the right policy mix.

"Income tax cuts are not much use to an individual with no income," Deutsche Bank economist Phil O'Donaghoe says.

"The case for business tax cuts stacks up better than the case for household income tax cuts."

Australian Associated Press