I'm not sure about W.A. regulations
But I bought an xtrail in NSW and I love in S.A and I had to take to the police an have them check the engine number against the vin number (at a cost) and take the relevant paperwork to the motor registration place and transfer the rego over to me (at a cost). I received new S.A. number number plates.
Hope this helps
It's a rigmarole! We purchased a second hand Nissan Navara ute and slide-on camper in November 2018 in Newcastle, NSW. Ute had 9 months NSW rego on it. In Batemans Bay we submitted the signed transfer form but it was not accepted as we didnt have a NSW address. About 2 weeks after arriving home to WA we applied online to transfer the ute. We found out we needed a 'Permit to move' the ute and and had to pay for two vehicle inspections - failed the first one because one of the rear fold down seats wasnt fixed in as the previous owner had temporarily removed it to insert an extra fridge. We replaced the seat correctly and had to pay for a second permit to move and the second inspection. We also 'lost' the 9 months rego paid for by the previous owner. With hindsight we should have kept driving it on NSW plates until closer to the rego renewal then gone through the WA transfer process. Regarding the Permit to move - someone in the licencing centre told us we had been driving it illegally since crossing the border into WA! As there is no WA licencing and inspection facility anywhere near the WA/SA border this was laughable! Good luck with changing your rego.