The longest and most complicated piece of legislation ever presented to the Assembly has been unveiled by the Welsh Government.
The grandly titled Land Transaction Tax and Anti-avoidance of Devolved Taxes (Wales) Bill creates a new Welsh tax to replace stamp duty on property sales.
It's the most significant money-raising power yet devolved to Wales. Stamp Duty currently raises £250 million a year from the sales of Welsh homes and business premises. We won't know the new tax bands and rates until the Finance Minister's budget statement next year and they will come into force in April 2018.
Stamp Duty is abolished in Wales from that date by the 2014 Wales Act, so the Welsh Government had to introduce a new tax or lose the revenue.
It's the most significant step so far in the process of giving Ministers in Cardiff Bay more responsibility for raising the money that they spend.
The tax won't be collected by HM Customs and Customs but by a new Welsh Revenue Authority.
The big test for the new system will come when - and if - the Welsh Government uses its powers to vary the rate of income tax.