I live in the U.S. I move to London. I live there for four years,
earning $350,000 per year. Then I return to the U.S. What are the
total national and local taxes I end up paying on my UK earnings? Do I
get any refunded when I leave? Do I pay any U.S. taxes?

Hello and thank you for your question.

A ggod starting point is the US-UK income tax treaty, which provides
in Article 14 that income earned in the UK from a US person's
employment there as you describe it will be taxed only by the UK and
not by the U.S.
UK-USA Tax Treaty
http://www.inlandrevenue.gov.uk/pdfs/ukusa_dtconvention.pdf

The UK maximum rate of tax is 40%.  The $350,000 income you describe
is about 200,000 pounds.  Of that nearly 5,000 pounds is covered  by
your personal allowance, nearly 2,000 is taxed at 10%, and nearly
30,000 is taxed at 22%, leaving about 163,000 to be taxed at 40%. 
Adding that up, the overall income tax on the income you describe
works out to about a 36% rate overall.
Income tax rates
http://www.inlandrevenue.gov.uk/rates/it.htm

You can budget about another 1% for national insurance
http://www.inlandrevenue.gov.uk/rates/nic.htm

There aren't any local taxes or sales taxes, except that a VAT tax has
been built into the pricetag of just about any goods you buy.  In
other words, one of the reasons that you'll find shopping more costly
than you're used to at home is the invisible VAT tax, which is
equivalent to a 17.5% sales tax in most cases.
VAT
http://www.netaccountants.com/vat.html

That should be all of the taxes on your employment earnings, and when
you return to the U.S. there won't be any additional taxes to pay.  If
you have other sources of income, for example interest, dividends and
capital gains earned on accounts outside the UK, you will be U.S.
income tax on these earnings but nothing to the UK (because although
temporarily resident in the UK you'll not be domiciled there.

Search terms used
income tax treaty london
UK income tax

I hope you find this information useful.  If you need to request
clarification, I would appreciate it if you will hold off on rating my
answer until I have a chance to respond.


Google Answers Researcher
Richard-ga

http://www.taxmeless.com/IRS593Publication.htm
Tax Highlights for U.S. Citizens and Residents Going Abroad
Don D. Nelson, Attorney & Certified Public Accountant

http://www.taxmeless.com/
http://www.protaxconsulting.com/html/us_expatriate.html

As a US citizen, I understand that you pay tax on your worldwide
income, regardless of location.

For the time you live in the UK you would be treated by the Inland
Revenue as ordinarily resident, and hence liable to UK taxes. My
understanding is that Income Tax and Capital Gains Tax are covered by
the UK/US double taxation treaty, so you would not be taxed twice- the
tax due to the lower taxing regime would be set against the tax from
the higher taxing one. Employment Income in the UK is generally taxed
at source so you would pay UK tax automatically.

You would for the period of UK residence have to comply with the
taxation requirements of both countries.