What's in and likely to be included in the budget:
Airports, roads and rails
The government will use "good" debt to finance a range of infrastructure projects. Top of the list is Sydney's second airport at Badgerys Creek. Following the Macquarie group's decision to forego first dibs on the airport in the city's west, the government will go it alone on the multi-billion project that will take nine years to complete. Also on its list is a reported $1 billion for the inland rail freight project linking Melbourne and Brisbane.
Expect more roads funding, especially for congested capital cities.
Agriculture
Farmers want to see the $1 billion for the Brisbane-Melbourne inland rail link as well as at least $60 million for the mobile phone black spot program, which prioritises community-identified areas. Labor wants the government to outline the cost of its push to decentralise federal government agencies from Canberra. It also wants to see the final bill for moving the pesticides authority to Deputy Prime Minister Barnaby Joyce's electorate, which it estimates to be as high as $60 million.
Climate action and energy
Little is expected in this area, as the government awaits recommendations from the Finkel review of energy market security and a year-long review of its climate policies. There may be a top-up for the Emissions Reduction Fund, which has a balance of less than $300 million - although on the recent trajectory that much could last for another two auction rounds. Funding for studies into a trio of hydro schemes come from ARENA's existing budget.
Defence
No surprises expected for Defence. Funding allocations are expected to follow trajectory set out in the 2016 Defence blueprint. Government likely to talk up shipbuilding in South Australia and Western Australia.
Foreign aid
Treasurer Scott Morrison has hinted the foreign aid budget isn't a target with $11.3 billion already been stripped out since 2013. In 2017-18 aid is expected to increase to $3.9 billion from $3.8 billion this year because of indexation in line with the consumer price index. Foreign aid is expected to hit an all-time low of 0.22 per cent of national income.
Foreign affairs
Diplomats from 28 agencies at Australian posts overseas could have their generous allowances trimmed after a sweeping review. Diplomats generally receive free accommodation while international school fees, babysitting costs, household expenses, wages for maids and drivers are also covered.
Health
The freeze on Medicare rebates that GPs are paid for bulk-billed consultations could come to an end earlier than planned in a bid to appease doctors and stymie Labor's Mediscare campaign. The freeze is due to be lifted in 2020, following its extension in 2014.
The government plans to encourage doctors to prescribe generic medicines, rather than big-name brands, which could save the budget $1.8 billion. That saving will be used to fund the listing of new medicines on the taxpayer-subsidised Pharmaceutical Benefits Scheme. The 2014 budget plan to raise the price of prescription drugs dumped.
Australia's first proton beam therapy centre will be built in Adelaide after the federal government committed $68 million to its establishment.
Housing
The government has been keen to play down what the budget will do to address affordability, despite raising expectations of a solution. It has flagged the establishment of a "bond aggregator" as an intermediary to attract greater private sector investment into affordable community housing. As well, there could be incentives to encourage older people to downsize in order to free-up family homes. Allowing first home buyers to tap their superannuation for a deposit appears to be a no-go idea, but a salary-sacrifice style savings account is on the cards.
Immigration and border protection
The looming closure of Australia's offshore immigration detention centre on Manus Island is expected to reap a whopping saving in the budget papers. The government is also expected to bank significant savings flowing from the refugee resettlement deal with the United States, with each detainee said to cost the country roughly $500,000 per year. There is also swirling speculation funding may be allocated in the budget papers for a mammoth Homeland Department-style agency to counter crimes including terrorism.
Meanwhile, migrants will be able to bring their parents to Australia for up to 10 years under a new temporary visa program. Citizens and permanent residents will be able to apply for the visa for five years at a cost of $10,000 and will then be able to renew it for another five years.
Media
Free-to-air broadcasting annual licence fees estimated to raise around $130 million will be abolished. Instead, broadcasters will pay new annual spectrum fees estimated to raise around $40 million.
There will be new restrictions to ban gambling advertisements from five minutes before the commencement of live sports coverage until five minutes after the conclusion of play or 8:30pm, whichever comes sooner. The government will provide funding of $30 million over four years to subscription television to maintain and increase coverage of women's sports and niche sports.
It will push ahead with plans to scrap the two-out-of-three rule that prevents a company controlling more than two of three radio, television and newspapers in an area. A rule which prohibits a proprietor from controlling a TV licence that reaches more than 75 per cent of the population will also be axed.
Schools
The government will pump an extra $19 billion into schools over the next decade under a plan labelled 'Gonski 2.0'. More than 99 per cent of schools will see a year-on-year increase in funding, and on average per-student funding will grow 4.1 per cent a year over a decade. Federal funding will grow from $17.5 billion in 2017 to $22.1 billion by 2021, and $30.6 billion by 2027. The per student base amount in 2018 will be $10,953 for primary students and $13,764 for secondary school students. About two dozen schools will lose some of their federal funding.
The budget will include a funding extension for the guarantee of preschool hours for four-year-old children.
Tax
Legislation for the third tranche of the government's 10-year corporate tax plan will be re-introduced to parliament in budget week. The two per cent deficit levy on higher income earners, introduced in 2014, will be removed as legislated. The budget will detail how much the tax office is reaping from measures aimed at combating multinational tax avoidance.
Possible small business package to include extension of $20,000 instant asset write-off.
Universities
The government got in a week ahead of budget day to unveil revamped measures from the controversial 2014 budget. Students will have to pay up to $3600 more for a four-year university degree and start paying back their loans as soon as their income reaches $42,000. The most expensive degree, medicine over six years, would cost $71,900, up from $68,000. Universities will be subject to a $2.8 billion efficiency dividend.
Welfare
Welfare recipients who persistently dodge their job-seeking obligations will be targeted through harsh punishments. The Turnbull team for weeks has proclaimed "enough is enough" for those who do the wrong thing, but has been silent on the proposed sanctions. The budget is also expected to contain funding for a swathe of more trial sites for cashless welfare cards, after two test runs showed positive results for problem gambling and alcohol consumption. Community groups want to see a raft of "zombie measures" contained in the 2014 budget finally taken off the table, and are urging action on housing and rental affordability.
'Zombie measures'
The government may dump some $13 billion in unlegislated savings, the so-called "zombie" savings measures, some of which have been stuck in the budget papers since 2014. Scott Morrison has said it is important the budget is a "credible and practical" document the government can put forward with confidence to the parliament.
