"See the chart on page 2 or 3. I will be self-employed and residing in Spain."

No one commenting (at the time I commented) is calling you a moron. The US tax code is really fucking complex. The more money you make outside the US and want to invest, the more you'll have to look at how and what you can invest in.

Several EU countries provide government subsidized investments for their citizens and residents. basically they are 401Ks/IRAs in country X. The US, however, does not recognize those contributions as tax free. You will have to both declare and detail those contributions (or pay someone to do it) and declare the interest as income on your US tax form.

Note as well as someone working self-employed. Yes, there is a double-taxation law, but it is not unlimited. There is also the "alternative minimum tax" that stopped getting adjusted for inflation a while ago, so you CAN end up getting double taxed.

The solution there is to form a local LLC. That will increase your tax preparation costs in Spain. It will also make you liable for some (IMO) illegal rules that came with Trump's tax changes in 2018.

Suffice it to say that you will have a lot of things to file on your US taxes as a US citizen abroad. Don't forget FATCA and FBARS either.

If you do take Spanish citizenship there are exit requirements and potential dangers if/when you visit the US in the future.

All that being said I think it is definitely a great choice you're making moving to Spain, for all the reasons you've posted on this subject.

The point of my post is for other people thinking aobut the same. There are a LOT of issues tax-wise to be considered.

I've been living in Austria as an ex-pat (with my own business) for 30 years. I've worked all over the EU (including 8 years in Spain) so I know what I'm talking about.