Last-minute budget leaks reveal the Federal Government is scrapping its promised 1 per cent company tax cut to help fund a $3.6 billion package for low and middle-income families and small businesses.

Treasurer Wayne Swan is calling his centrepiece the "benefits of the boom" package, and combined with the reworked education tax refund - now a direct school kids bonus payment - it will deliver $5 billion over four years.

The company tax cut was promised as part of the Government's mining tax. The Coalition had opposed it, while the Greens were against the part of the cut going to big business.

Now small businesses will get the $6,500 instant asset write-off announced in the mining tax and the loss carry-back tax break, which allows businesses to write off losses against previous profits.

The Government still wants to deliver a company tax cut, but it will be up to business to find the savings from its own area if it wants the tax cut to go ahead.

The surplus in 2012-13 is forecast to be $1.5 billion, rising to $2 billion the year after, $5.3 billion in 2014-15 and $7.5 billion in 2015-16.

There will be $1 billion over four years, most at the back end, for the National Disability Insurance scheme and $250 million for e-health initiatives.

What to expect in tonight's budget: $500 million for dental care for disadvantaged patients and those on the public waiting list.

$500 million for dental care for disadvantaged patients and those on the public waiting list. School Kids Bonus, which replaces the Education Tax Refund, giving parents cash payments of $820 if they have a child at high school and $410 for a child at primary school.

School Kids Bonus, which replaces the Education Tax Refund, giving parents cash payments of $820 if they have a child at high school and $410 for a child at primary school. The carry-back measure for small businesses allowing them to use past profits to offset current losses by up to $1 million.

The carry-back measure for small businesses allowing them to use past profits to offset current losses by up to $1 million. Funding for a National Disability Insurance Scheme.

Funding for a National Disability Insurance Scheme. Cuts of $5 billion over four years to Defence.

Cuts of $5 billion over four years to Defence. $1 billion in savings made by increasing the superannuation contribution tax for high-income earners.

But there are more cuts.

The commitment to raise overseas aid spending to 0.5 per cent of gross national income will be deferred for a year to 2016-17.

While aid will still grow, aid groups will be unhappy with the deferral.

The package was promised by former prime minister Kevin Rudd as part of the Millennium Development goals.

It does aid the budget bottom line substantially to the tune of $2.9 billion.

While it is delivering cash benefits to low and middle-income earners it is hitting the rich, ending the away-from-home allowance which goes mostly to business executives, after one year, saving $1 billion.

Cracking down on golden handshake payments will save nearly $200 million.

Mr Swan is selling this as an "old-style Labor budget" - coming back to surplus to allow the reserve bank room to cut rates and delivering benefits to low and middle-income earners to ease the cost of living.

All up a family earning $85,000 a year with one child in high school and one in primary school will get $1,830 in upfront payments and that does not include the tax cuts and increased benefits being delivered as part of the carbon tax.

While the Opposition is likely to criticise the payments as part of the "carbon tax bribe", the Government is questioning whether the Coalition can afford to vote against them.