A multi-billion-dollar reconfiguration of the Coalition's seven-year tax plan to favour low- and middle-income earners will be at the heart of Treasurer Josh Frydenberg's first Federal Budget.

Key points:

Tax cuts favouring low- and middle-income earners will be brought forward

Tax cuts favouring low- and middle-income earners will be brought forward About 10 million Australians will receive tax relief in today's budget

About 10 million Australians will receive tax relief in today's budget Those aged 65 and 66 will also be able to make voluntary superannuation contributions

The ABC understands the Morrison Government will today unveil a reshaping of its already legislated tax plan, with tax cuts favouring low- and middle-income earners to be brought forward.

This will be on top of the $530 tax offset to be received from July 1 for the 4.4 million workers earning between $48,000 and $90,000 that formed part of phase one of the plan.

Those on incomes between $37,000 and $126,000, or about 10 million Australians, will receive tax relief in today's Budget.

On this basis, a mooted "bring forward" of phase two of the Coalition's tax plan, which would increase the 32.5 per cent tax bracket from $90,000 to $120,000, will not happen.

As one Coalition figure put it, the Government wants to avoid a "top hats versus hard hats" political argument that plagued former Liberal prime minister Malcolm Turnbull in the 2016 election campaign.

This is legislated to occur in July 2022, and Government sources say this date will not be brought forward given its greatest beneficiaries would be those earning over $150,000.

Increasing the 19 per cent tax bracket from $37,000 to $41,000 and increasing the low-income tax offset from $445 to $645, also currently scheduled for July 1, 2022, would deliver up to $310 a year from July if brought forward.

Mr Frydenberg's Budget will forecast a surplus for 2019-20 and have billions of dollars allocated to infrastructure projects nationwide.

The Budget will also contain a $75 million measure to allow 65- and 66-year-olds to make voluntary contributions to their superannuation without having to meet a work test.

The current rule requires people aged 65 and over to work for a minimum 40 hours over a 30-day period in the relevant financial year.

This test will be scrapped for those aged 65 and 66.