Social Security income is added to other income on the tax return in order to determine taxability and there is no tax due on certain income thresholds according to filing status. An American citizen must report all income from within US and outside US on their individual income tax return. There are exclusions available for circumstances where they are employed in another country. I would need more information to further advise. If American citizen has a foreign bank account they would be required to file additional forms and provide financial institution information following the new FBAR (Foreign Bank Account Report) form with the Department of the Treasury.