1) Taxes on Bitcoin sales do not get automatically deducted in any European country, you will have to file tax reports yourself.
So the banks don't rat you out as the U.S. banks do?
2) Taxes vary wildly between EU member states. Not just in regards to crypto. Be aware that the tax-free-after-1-year-of-holding rule only applies to a handful of countries (eg. Germany, Austria,... not sure where else). Selling before the 1 year holding is usually taxable as income tax (which also varies wildly between member states), selling after the holding period is usually taxable as capital gains tax (or not at all, if you're lucky). Either way, look closely into how each country handles taxation.
Yes, I know. Assuming it's one of the countries that do that, how would reporting work? I don't think you'd have to report then, right? Why do you say "if you're lucky?"
3) In which country you bought the Bitcoin originally doesn't matter. You should be able to prove holding time though. Arguably referring to the blockchain may suffice, but as far as I know there has been no precedence on how to report holding time correctly so far -- and you can also expect that what counts as proof for holding time will vary wildly between EU member states.
Well, has anyone reported time so far? Has it worked? What's the point of guidance on these things if a tax payer can't report it properly or it won't get accepted?
4) You pay tax in the country you reside in, assuming you have already taken full residency and have become a tax resident. At which point you become a tax resident depends on the country you move to and likely also where you are originally emigrating from (ie. immigrants from non-EU member states have to follow different rules than immigrants from EU member states. I wouldn't be surprised if there's a set of rules specifically for immigrants from the US). Prepare for paperwork as you likely won't become a tax resident automatically, but also will need to become a tax resident at one point to be allowed to legally stay there for a prolonged period of time -- assuming you don't have citizenship already.
That sounds insanely complicated... I have no idea how to go about this.
It really depends on the countries involved. My firm works A LOT with international taxpayers and foreign investors, but as is typical with most US CPA firms, we handle the US reporting and work with a sister firm in the other country to handle reporting in that country. The EU hasn't negotiated a single tax treaty with the US. Instead, it's on a country-by-country basis. I have clients throughout Europe in common business-partner countries (UK, Ireland, Germany, France, Netherlands, Luxembourg, Switzerland, etc.). It adds an extra dimension of complexity and compliance to the US tax reporting. Common reports and forms include FBAR, Forms 8938, 3520, 5471, W8-BEN, and 1042.
Which firm is this? Maybe I should consider using such a firm in the future when I want to cash out. I, personally, intend to "lose" certain citizenships. I'd need guidance on doing this and dealing with crypto in the future.