The reporting comes in two separate pieces, and having one does not excuse the other. The first is the FBAR, the Report of Foreign Bank and Financial Accounts, filed with the Treasury's Financial Crimes Enforcement Network when the combined value of a person's foreign accounts exceeds $10,000 at any time during the year. The second is Form 8938, filed with the tax return under the Foreign Account Tax Compliance Act, at thresholds that are higher than the FBAR's and that vary with filing status and whether the person lives abroad. Many people with offshore accounts must file both and report the same accounts on each. On top of the reports, the income earned in the account, interest, dividends, gains, is taxable on the US return like any other income.
The institutions themselves now report, which is why hiding an account has become impractical. Under FATCA, most foreign financial institutions identify and report accounts held by US persons to the Internal Revenue Service, either directly or through agreements their governments signed with the United States. So the government generally learns about a foreign account from the bank even if the taxpayer says nothing. The era in which an offshore account was a reliable hiding place is largely over, which changes the calculus: the practical choice is not between reporting and secrecy but between reporting and being caught not reporting.
The legitimate reasons to hold one are numerous and ordinary. Living or working abroad requires a local account for salary, rent, and daily expenses. A person who owns property in another country needs somewhere to receive rent and pay upkeep. Someone running a foreign business, holding a foreign inheritance, or simply wanting to hold another currency has a real reason for a foreign account. None of these involves tax avoidance, and all of them are fully compatible with the reporting rules. The account is a tool; only its concealment is a problem.
The penalties fall on the failure to report, and their size is the reason to take the reports seriously. A non-willful failure to file the FBAR carries a civil penalty adjusted for inflation each year, while a willful failure can reach the greater of a larger statutory amount or 50 percent of the account balance, plus potential criminal exposure in the worst cases. Missing a required Form 8938 carries its own penalties and can keep the return's statute of limitations open. For a taxpayer who realizes they have unreported accounts, the Internal Revenue Service maintains voluntary-disclosure procedures, including streamlined procedures for non-willful cases, that allow the accounts to be brought into compliance on defined terms rather than waiting to be found.