Jim Chalmers has already revealed a $12.7 billion blowout in "unavoidable" spending, half of which was due to natural disaster relief proving more costly than anticipated.
The budget update on Wednesday will also spend billions on election promises the government wants to fulfil.
The majority of the $13 billion-odd set aside for campaign commitments will go to the states and territories to build up to 100,000 new homes exclusively for first home buyers.
To help make ends meet, Dr Chalmers revealed on Sunday he had booked $20 billion in savings across the next four years.
"We've now found savings in every single one of our seven budgets and budget updates," he told Sky News.
"This mid-year budget update will be defined by economic responsibility, just like the government is."
He downplayed expectations of fresh announcements, saying it "was not a mini-budget, there's not a lot of new stuff in there".
Dr Chalmers has already ruled out extending energy rebates beyond the current year, while changes to deeming rates will give a haircut to the pension payments of asset-holding retirees.
The squeeze is also on federal department spending, leaving the central question how it impacts the bottom line of government books.
AMP chief economist Shane Oliver predicts the budget deficit in 2025/26 will narrow from the $42.1 billion forecast in the March budget to about $37 billion, courtesy of company and personal income taxes continuing to exceed Treasury's expectations.
Veteran budget-watcher Chris Richardson has predicted a near-$10 billion improvement in the bottom line for the financial year, putting his expected deficit at $32.6 billion.
Mr Richardson expects the improvement to come from a $14 billion upgrade to revenue, driven by stronger tax takes on high-performing super funds and partly offset by a $4 billion increase in spending.
He predicts the headline deficit, which includes "off-budget" spending the government uses to squirrel away items loosely classed as investments, will come in at $55.7 billion.
The budget documents will also include Treasury's updated forecasts for economic indicators such as inflation, unemployment and GDP growth.
They should include upward revisions to price growth after the inflation dragon came back to life in the September quarter.
Dr Chalmers has also said to expect an upward revision to business investment forecasts, from 1.5 per cent to three per cent growth this financial year, reflecting a stronger-than-expected build-out of data centres.
There is little other official economic data to expect in the coming week as Christmas approaches.
The Westpac-Melbourne Institute consumer sentiment survey on Tuesday is likely to show a large drop in confidence in response to comments from Reserve Bank governor Michele Bullock essentially ruling out further interest rate cuts.
From markets a few months ago pricing in one or two more cuts in 2026, expectations are now for one or two rate hikes instead.
RBA officials Andrew Brischetto and Brad Jones will speak on Monday and Tuesday, respectively, although their addresses are not expected to shed new light on the direction of monetary policy.
In the US, markets closed down on Friday amid fears of a bubble in AI-linked stocks.
The Dow Jones Industrial Average fell 245.96 points, or 0.51 per cent, to 48,458.05, while the S&P 500 lost 73.59 ‌points, or 1.07 per cent, to 6,827.41.
The tech-heavy Nasdaq Composite lost 398.69 points, or 1.69 per cent, to 23,195.17.
Australian share futures were down 51 points, or 0.59 per cent, to 8,659.
Stocks finished higher for the week on the back of mining gains, with the S&P/ASX200 rising 105.3 points on Friday, or 1.23 per cent, to 8,697.3, as the broader All Ordinaries gained 105.8 points, or 1.19 per cent, to 8,983.3.
