US Treaty Resident with US-only Income & SA 106

I am retired UK & US dual citizen who moved to USA 40 years ago. As such I am US treaty resident (TR). All of my income (Interest, Dividends and Capital Gains) is from the US stock market. I may spend enough time on holiday in the UK this year to trigger UK residence too, so requiring me to file Self-Assessment as ‘resident’. As US TR, will I pay any UK tax on my US income paid to me in USA and taxed by USA? For example assume US Interest, Dividends and Capital Gains each in the amount of $20,000 How should I enter these on SA106?

Hi,

If you are UK tax resident and domiciled, you will be liable on your worldwide income. You can see guidance here:

Tax on foreign income

Thank you.

What about income from a Traditional IRA - say I sell $20k of fund shares in my IRA - is that taxable in UK too or covered by the treaty?

Hi
Payments made by the individual into an IRA, are made after tax relief is given to the individual by the employer.  
Payments from this pension are taxable in the USA.  
HMRC do not recognise IRA schemes as pensions, so for UK residents, they are taxed as income under the interest and declared as foreign interest on a tax return (SA106).
Please also refer to the double taxation treaty with USA - USA: tax treaties