I'm thinking of how to do my taxes when I take distributions from my IRA as a US/UK dual citizen residing in the UK. Here is what I've come up with, I'd love comments and critiques from anyone with actual experience of doing this and anyone who's just interested that can correct my errors.
The UK has primary jurisdiction over taxing retirement distributions because of the tax treaty Article 17, but as I'm a US citizen the US retains it's right to tax those distributions (Savings Clause), but lets me take a tax credit for any foreign tax paid (Relief from Double Taxation, Article 24). So the practical upshot of this is:
file a W-4P with my IRA provider and claim 10% US mandatory withholding. I don't have a US residence address so can't claim withholding exemption;
do the UK self assessment (SA-100 and SA-106) and pay whatever tax is due as a UK resident as if the IRA were UK sourced;
file US 1040, form 8833 to claim the treaty, and a foreign tax credit form 1116.
So if the US tax rate is 20%, and remembering that 10% has been withheld already, and the UK rate is 30% I'd be able to take a max tax credit of 20% on my US return making a total tax paid in the US of 30% and I'd get the excess 10% due to the withholding as a refund. So no tax paid to US and the total tax paid is the 30% UK rate as it is the higher of the 2 rates.