About 60 per cent of the benefit from Treasurer Scott Morrison's 10-year tax cut plan will go to the top 20 per cent of income earners by the time it concludes in 2027, according to modelling by the Australian National University.

The first two stages of the three-step tax plan from 2018 to 2024 will more or less deliver on Mr Morrison's budget pledge to "protect low and middle income earners". Next year, for instance, the top 20 per cent of households will receive only 31 per cent of the benefits with the rest going further down the scale.