Most people who get foreign account reporting wrong don’t get it wrong about their main bank account. They get it wrong about the accounts they stopped thinking about: the student account from before they emigrated, the savings account with a few hundred dollars left in it, the account their spouse manages that has their name on it somewhere.

The reporting rules were written to catch exactly those accounts. Three mechanics do the catching.

1. The threshold is aggregate, not per-account

The main foreign account report — the FBAR — is triggered when the combined value of all your foreign financial accounts exceeds US$10,000 at any point during the year. Not $10,000 per account. All of them, added together, at their highest moments.

Run the math on an ordinary expat life: a checking account that peaks at $6,000 around payday, a savings account holding $3,500, an old account back home with $900 in it. No single account looks reportable. Together they cross the line — and once the threshold is crossed, every account gets reported, including the $900 one.

The aggregate rule means “none of my accounts is big” is not the test. The test is whether your whole foreign financial footprint, at its peak, cleared $10,000 even briefly. A bonus landing, a house-sale deposit passing through, a transfer sitting in the wrong account for a week — any of these can put an otherwise unremarkable year over the line.

2. Dormant doesn’t mean invisible

There is no activity requirement, no minimum balance, and no “I forgot it existed” exception. The account you opened at nineteen, the one tied to an old employer, the joint account with a parent that you’ve never once touched — if it’s a foreign financial account and you have a financial interest in it or signature authority over it, it counts toward the aggregate and belongs on the report.

Forgotten accounts are also where the explanations get hardest later. Leaving your largest account off a report has an innocent reading. A pattern of unreported accounts across multiple institutions and years reads worse — patterns are precisely what enforcement looks at when deciding whether a failure was an honest mistake or something more. Checking “No” on the Foreign-Accounts Question — How One Checkbox Becomes Evidence Against You covers a closely related version of this problem.

The practical fix is boring and effective: once a year, list every foreign account with your name attached — every bank, every country, including the ones you’d forgotten. The list takes an evening. Reconstructing it under examination takes considerably more.

3. Joint accounts with a non-US spouse: the full value, not your half

This one surprises nearly everyone. If you’re a US person and you jointly own a foreign account — with anyone, including a spouse who has no US status at all — you report the entire value of the account. Not your half. Not your contribution. The whole balance.

Your spouse being outside the US system doesn’t shrink your reporting. The rules follow your interest in and access to the account, and joint ownership gives you a financial interest in all of it. A US person whose non-US spouse keeps the family savings in a joint account can have a six-figure reporting obligation attached to money they never deposited and never touch.

Two boundaries keep this from being worse than it is. First, your spouse’s individual accounts — the ones you don’t own jointly and can’t sign on — are not your problem; no financial interest and no signature authority means no reporting. Second, married couples can sometimes consolidate onto a single report when all of the non-filing spouse’s reportable accounts are jointly held, using the proper authorization form — a convenience worth asking a professional about, with conditions attached.

The mistake pattern here is assuming “it’s really my spouse’s money” or “they report it in their country” settles the US question. It doesn’t. The US question is only ever about your name, your access, your interest.

Why this is worth an evening of your time

Foreign account reporting is informational — filing it costs nothing in tax. Failing to file it is where the costs live, and they’re calculated in ways that punish exactly the multi-account, multi-year drift this article describes. The Math Nobody Runs: What Compliance Costs vs. What Non-Compliance Costs puts numbers to that asymmetry, and the recent enforcement cases — The $12 Million Paperwork Penalty: What the Schwarzbaum Case Means for Anyone With Foreign Accounts among them — show how large the stakes can get when accounts stay hidden for years.

If you’re reading this and mentally inventorying accounts you’ve never reported: that’s the right instinct, and there are established paths for catching up that work far better when you start them than when the IRS does. Can I Just Stop Filing? Why Ignoring US Taxes Abroad Backfires covers what catching up looks like.

This article is general educational information, not tax advice. Cross-border situations turn on individual facts. Before acting on anything here, speak with a qualified cross-border tax professional about your specific circumstances.