Complex sentence: Devolution of tax-raising powers is to begin with smaller taxes such as Stamp Duty in 2018, and by 2020 the Welsh government is to have the power to vary income tax, following a referendum.
Split into simpler sentences: Devolution of tax-raising powers should begin with smaller taxes such as Stamp Duty. By 2020 the Welsh government should have the power to vary income tax, following a referendum.