The United States can tax any and all income on its citizens, regardless of whether the income come from local or foreign sources. U.S. citizens must fill out IRS Form 8938 if they hold foreign stocks or securities that pass the reporting threshold (specified foreign assets valued at minimum USD $200,000 on the last day of the tax year OR USD $300,000 at any point of the year for unmarried taxpayers; specified foreign assets valued at minimum USD $400,000 on the last day of the tax year OR USD $600,000 at any point of the year for married taxpayers). U.S. taxation on foreign stock options should be taken seriously. We recommend to consult a tax professional if there is any question of whether to report financial assets.