What we already know about the budget

WHAT WE KNOW SO FAR ABOUT TUESDAY'S BUDGET

* Economists predicting MYEFO forecast of $31.2 billion for 2015/16 deficit to blow out to upwards of $40 billion.

* Treasurer Joe Hockey promising "quality trajectory back to surplus". But no surplus likely in the forward estimates.

* Fall in iron ore prices to impact on tax receipts for 2015/16

* Record infrastructure spend, as states take advantage of asset recycling scheme bonus payments

* Crackdown on welfare cheats through better data matching to identify fraud, and $1 billion Centrelink computer upgrade to help with crackdown.

* Major $3.5 billion reform to child care, with single payment paid directly to childcare centres to reduce parents' upfront costs. Stay-at-home parents with a family income more than $65,000 will no longer secure childcare subsidies.

* Income-tested hourly subsidy for nannies for 10,000 shift worker families in a two-year trial costing $246 million.

* Loophole that allows new parents to claim paid parental leave payments from both the federal government and their employer will be closed, saving nearly $1 billion a year.

* Plans for a $20 billion medical research fund to go ahead

* Pharmaceutical Benefit Scheme changes to save about $3 billion over four years. Comes via removing subsidies from a raft of over-the-counter medicines. Health savings likely to total $7 billion over forward estimates.

* Government to fund $1.3 billion worth of new generation cancer drugs over four years through listing on the PBS.

* $6 bonus for doctors to prompt parents to immunise their children will be doubled to $12. Objectors to immunisation will not be eligible for welfare and childcare benefits.

* Almost $300 million for mental health services

* $200 million for dental health care

* No changes to superannuation this term

* Tighter access to age pension. Part-pension assets test (excludes family home) will be cut to $820,000 for couples.

* $128 million over four years for a financial crimes task force

* Global companies to face tighter laws on shifting profits to foreign tax havens. First tranche of this is expected to reap money in forward estimates.

* Tax cuts for business. 1.5 per cent for small business.

* Drought package including $250 million for the drought concessional loan scheme in 2015-16, and $35 million to boost economic activity in badly hit towns and regions.

* An extra $40 million to upgrade airstrips and boost air services for remote communities.