The first Wales-only taxes for 800 years have come into effect.
Two new devolved taxes have been introduced – the Land Transaction Tax (LTT) on property, which replaces stamp duty, and the Landfill Disposals Tax (LDT), which replaces landfill tax.
The money raised would make a “very significant contribution to Welsh public services”, according to the head of Wales’ new tax-collecting body.
Ministers estimate the taxes will raise more than £1bn over four years.
Powers over stamp duty and landfill tax were transferred from Westminster to Cardiff Bay under the Wales Act 2014, and the Welsh Assembly legislated for their replacements.
It also created the Welsh Revenue Authority (WRA), to manage and collect the taxes on behalf of the Welsh Government.
WRA chief executive Dyfed Alsop said it was an historic moment.
“It’s something that stays in Wales. It’s for Wales, made in Wales and remains here,” he said.
Mr Alsop said most of the Welsh public would not deal with the WRA, unless they were buying a property and working with a conveyance or a solicitor for example.
“The big difference for people is that these taxes will be collected by the Welsh Revenue Authority and that they go to be used for spending on public services in Wales.
“The Welsh Government’s estimate how much money these will raise is something in the order of £1bn over the first four years – so that makes a very significant contribution to Welsh public services.”
The Welsh Revenue Authority is a non-ministerial department of the Welsh Government, made up of 70 members of staff, based in Treforest outside Pontypridd.
It says it will help deliver a fairer tax system for Wales and offer services, including bilingual and digital.
“What we’re here to do is work closely with the public, work closely with those people who need to pay those taxes, to make sure that we make it as easy as possible, we’re as supportive as possible,” Mr Alsop said.
“I think that helps engender a sense of trust, and it helps create the feeling that things are being done in a fair way.”
New powers for the Welsh Assembly also came into force on Sunday.
The Wales Act devolves extra responsibilities for transport, energy and electoral arrangements.
It also defines what is under the control of Westminster, with everything else assumed to rest with the assembly – known as the “reserved powers” model.
Welsh Secretary Alun Cairns said: “From decisions over ports, taxis and bus regulation and teachers’ pay, to decisions on the electoral system for the assembly and Welsh local government, all these decisions will now be taken in the Senedd”.
“To me that is responsible devolution; that is real devolution and I think that is vital for Wales and for the UK.”
The Conservative UK cabinet member called on the Labour Welsh Government to be “innovative with the opportunities these new powers provide and deliver the improvements in devolved services that the people of Wales deserve”.