@MarkLondon , assuming that you ( plural ) and your dependent child are all US citizens , US tax laws apply as if you were residing in the USA -- world income taxed by the USA. Thus that your son is considered a resident ( ordinarily resident or currently domiciled ), is not material for US tax purposes. That he spends 3/4 of the year ( he is not with a visa , right ? ) in the USA makes him also ineligible for excluding his foreign earnings -- physical presence rules apply and not domiciliary rules. Give that he is under 24 and going to school, he is still your dependent and files his US return as a dependent and is taxed on world income. If UK taxes him on the UK sourced income then that "foreign" income and the taxes thereon would be eligible for foreign tax credit, ameliorating the burn of double taxation.
Does this make sense? Do you need more help on this ?
pk
