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If you worked in the US and were paid in the US and paid in US $'s - you pay US taxes.





If you had gone to UK and got paid while working there then you would first file in the UK and pay them any taxes you owe them but then you would still need to report this income to the IRS and pay US taxes on it. It might get reduced by the amount of UK taxes paid.





The US taxes US citizens on any income you make anywhere in the world.




I believe the USA if you worked in USA.