Per the Bank Secrecy Act, every year you must report certain foreign financial accounts, such as bank accounts, brokerage accounts and mutual funds, to the Treasury Department and keep certain records of those accounts. You report the accounts by filing a Report of Foreign Bank and Financial Accounts (FBAR) on Financial Crimes Enforcement Network (FinCEN) Form 114.
For full instructions and Who Should File, please see: Report of Foreign Bank and Financial Accounts (FBAR) | Internal Revenue Service