The question remains on whether you paid tax on the 2017
crypto earnings under your previous residency? Or did you just leave your last country, take up residency in UK and now want to cashout (outside UK) having not had the money taxed beforehand?
Points to take into account. The UK tax year starts April 6th 2018. If you registered in UK after this date but cashed out crypto before that date then the gains occurred in the previous tax year when you were not resident in the UK and hence its considered as capital. Therefore it would not be subject to any UK tax when those funds are remitted to the UK to buy property. However if you become officially registered after April 6th and cashout after April 6th then if you bring that money into UK to buy property its going to be considered foreign capital gains. You will then be taxed on it if you remit it to to the UK. You see the dilemma you could face?
The first thing you need to do is ensure all your crypto gains are documented properly. If the millions you have came about via capital gains of
cryptocurrency i.e you held crypto and it increased in value and you sold it later and made a gain then document this carefully. You need to keep solid proof of when you purchased and when you sold.
Ok so now that you are in the UK and want to reside as a resident non-domicile you need to inform HMRC. It is wise to get in advance tax ruling when applying. Recruit the services of a proper law firm...don't save on the pennies here. As I mentioned above timing is important. Bringing the money into the UK will be an issue if not done correctly. Pay attention to when you became resident and when you cashed out. You should
cash out before becoming resident to avoid remittance tax. Once your on the remittance basis there are different tax rates for capital and income remitted to UK. You need to carefully separate money you hold offshore that is capital from that which is income. I cannot emphasize this enough!!!! If you were to mix income into the capital account for example then you end up with dirty capital and it becomes a tax mess when you want to bring that money into the UK. However if you are bringing all the money in one time and keeping nothing offshore then this is not an issue. However my advice is only bring into the UK what you need and keep the rest offshore. UK has high taxes. You can put the money to work offshore in a zero tax environment like every other resident non-domicile does.
Definitely engage a serious law firm like Withers Law to get the timing and calculations right. Forget about internet cheapo firms as getting this wrong will mean you could get hit with a 45% tax bill.
Enjoy the UK, with money you can live very good