Most tax systems attach to where you live. The US system attaches to who you are — and it turns out a surprising number of people are US persons without ever having decided to be.

They’re sometimes called accidental Americans. The accident is usually one of three kinds.

The three quiet doorways

Born on US soil. Birth in the United States has historically conferred citizenship in ordinary cases, subject to narrow exceptions and any current legal developments — including a birth that happened because the nearest hospital to a Canadian border town was on the American side, or because parents were briefly working in the US. The person may have left as an infant, never held a US passport, and speak of “the States” as a foreign country. If citizenship was acquired, U.S. tax status generally came with it.

Born to a US parent abroad. Citizenship can also transmit by descent. The rules here have conditions — they’ve changed over the decades and depend on the parent’s own history — so this doorway is genuinely uncertain for many families rather than automatic. But plenty of people raised entirely outside the US are citizens by descent and have never checked.

A green card that never formally ended. This one catches people who know they were once connected to the US and believe they cleanly left. For tax purposes, lawful permanent resident status generally persists until it is formally abandoned or revoked — not merely allowed to gather dust. Tax-treaty positions can complicate this, but they do not make a green card disappear as an immigration document. Someone who held a green card, moved home years ago, and let the card expire in a drawer may have remained a US tax resident the entire time. Expiry of the physical card and termination of the status are different events.

Why it surfaces now, and how

For decades, an unknowing US person abroad could live a whole life without the question arising. What changed is bank reporting: foreign financial institutions now identify accounts held by US persons and report them to the US. The discovery moment, in practice, is often a letter from your own bank — asking about a US birthplace on file, requesting a US tax number, occasionally threatening to close the account.

That letter tends to arrive with a jolt, because it retroactively reframes decades: the obligations of a US person — worldwide filing under the system explained in I Moved Abroad — Do I Still Have to File US Taxes? , plus the account-disclosure regime in The Second Filing System: US Disclosure Forms Most Expats Never Hear About — may have applied for years.

What the discovery does and doesn’t mean

It doesn’t mean decades of back taxes are automatically owed; many accidental Americans would have owed little or nothing in tax. It doesn’t mean panic-filing everything at once, which has its own hazards. And for those who ultimately choose to formally exit, the government fee for renouncing citizenship was sharply reduced effective April 2026 (Renouncing US Citizenship Now Costs $450 — Here’s What the Fee Cut Doesn’t Change) — though renouncing addresses the future, not the past.

What discovery does mean is that the status question deserves a definitive answer — parent’s history, birthplace, immigration record — before any filing strategy is chosen. Whether someone is a US person is a facts-and-documents question, and it comes first. Everything else is downstream.

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