Sources: IRS, US citizens and resident aliens abroad; IRS, US citizens and residents abroad filing requirements; IRS, About Publication 54; Treasury and IRS, Foreign Account Tax Compliance Act; FinCEN and IRS, Report of Foreign Bank and Financial Accounts (FBAR); IRS, Expatriation Tax; IRS, Instructions for Form 8854. This is a simplified planning illustration, not legal or tax advice — a second passport or foreign tax residency does not by itself end US filing obligations.