Experts have analysed the true costs of the Government’s new tax plan.

The Federal Government wants to shake-up Australia’s tax system with a seven-year plan to cut tax and simplify brackets.

Treasurer Scott Morrison says workers on $160,000 will see a proportional reduction of 2.4 per cent, while those on $50,000 would see a 6.3 per cent reduction.

The largest reform comes in 2024, when the 37 per cent tax rate is eliminated.

The Government has not detailed the estimated cost of the plan after 2024.

The Australian National University has modelled the tax cuts and found that despite being framed as targeting low and middle income earners, they will actually provide the most benefit to the highest earning Australians.

The modelling found that by 2027, a couple with two children earning over $130,000 a year will be bank up to $8000 in extra cash.

It means a 2.2 rise in income for workers in the highest quintile, 1.1 per cent for those in the middle quintile and a 0.2 per cent rise in the lowest bracket.

The assumptions were based on 10-year forecasts of wage movements and the make-up of quintiles.

“I think what it shows you quite clearly is most of the benefits [from the tax cuts] go to high-income families in the later years,” ANU professor Ben Phillips told Fairfax.

“Largely because it is high income families who pay the tax, it is very much skewed towards the high end.”

The new tax rates go beyond those recommended by former Treasury secretary Ken Henry - who suggested a drop to 35 per cent.

Mr Morrison confirmed the total cost of the package would be $140 billion over a decade but has refused to outline a year-by-year breakdown.

KPMG modelling has found the cuts will cost $17.8 billion per year in 2016 dollars after 2024.

KPMG economics partner Brendan Rynne says the tax plan could reduce the personal income tax take by about 5 per cent.

“The reality is it is quite appropriate policy,” he told reporters.

“The fact that there is staggered tax relief for personal income tax that matches our desire to pay down net government debt that has accumulated as a consequence of continual deficits is appropriate.”