People with lots of financial assets overseas must attach Form 8938 to their 1040s. Taxpayers filing jointly who live in the U.S. must submit the form if the value of their foreign financial assets topped $100,000 on Dec. 31 or $150,000 at any time during 2018. These thresholds are halved for singles and are much higher for filers who live abroad. Foreign financial assets include foreign investment assets, offshore accounts, foreign pensions, interests in foreign businesses and more. The cost for failing to file the 8938 is rather steep: A penalty of $10,000

The filing date for owners of foreign accounts is April 15. U.S. taxpayers with foreign financial accounts whose total value exceeded $10,000 at any time in 2018 are required to electronically submit FinCEN Form 114 to report the offshore accounts. Filers who miss the deadline get an automatic six-month extension to file the form. Make sure to comply with these rules. Battling offshore tax evasion is an IRS priority.