I have a friend resident in the UK who is, like me, a UK/US dual citizen. She has recently started a job that offers a pension and has been looking into ISAs and investments for her and her kids. I had a long email from her complaining about the frightening complexity of doing her US and UK taxes. I told her to forget the ISA, stay away from all UK mutual funds and get some professional advice to deal with the UK pension on her US tax return. She made a very telling remark in reply. She said
"I'm thinking about giving up US citizenship. I'm worried I'm going to get my taxes wrong. I'm not doing it to avoid taxes, but to make sure I pay the right amount without spending lots to get them done".
I thought about this and it's definitely correct that her taxes would be far simpler as only a UK citizen as she has no money in the USA. I also looked at my situation. I have lots of retirement accounts, a pension and SS in the USA as well as after tax investments and as a US/UK dual citizen living in the US my taxes are relatively simple....at least Turbotax handles them. But if I move to the UK my taxes will become pretty complex, mostly because of the savings clause in the treaty. But as only a UK citizen living in the UK the savings clause goes away and my US SS and retirement accounts won't be taxed in the US, thank you W-8BEN and Article 17, and I'll be free to move my taxable investments to the UK. I'll only have to deal with UK tax on those as well, also no FATCA, FBAR or PFIC.
It really is a sad thing when someone feels so frightened and intimidated that to make sure they pay their taxes correctly they'll consider giving up US citizenship. It's the opposite of expatriating to avoid taxes, it's expatriation so they have a chance to comply with the tax rules.