The US side starts at the green card, not at naturalization
Under IRC §7701(b)(1)(A)(i), lawful permanent resident status alone makes someone a US tax resident, with worldwide income, FBAR, and Form 8938 obligations, from the first day of US presence as a lawful permanent resident. Naturalization years later does not create new exposure; by the time it happens, the person has typically already been a full-scope US taxpayer for the three years of permanent residence and marital union required for the spousal naturalization track, whether or not any US return was ever filed for those years. See the general breakdown of this mechanism for how it applies beyond Korea.
Do you have to give up Korean citizenship?
Yes, and it is automatic, not a choice made afterward. Korea's Nationality Act, Article 15(1), provides that a Korean national who voluntarily acquires a foreign nationality loses Korean nationality at the moment of that acquisition. Taking the US Oath of Allegiance is a voluntary act, so Korean nationality is lost the instant the oath is completed, not on some later date and not only if reported. Article 15(2) separately allows a six-month window to declare an intent to keep Korean nationality for people who acquire a foreign nationality involuntarily, covering categories like automatic spousal or adopted-child nationality granted by another country's law without an application; that provision does not apply to US naturalization, which always requires an affirmative application and oath.
What the loss-of-nationality report actually does
Korean law separately requires filing a loss-of-nationality report (국적상실신고) with the Ministry of Justice, generally through a Korean consulate, under Article 16 of the Nationality Act. Korean-language reporting on this describes real, ongoing cases of naturalized Korean-Americans delaying or avoiding that filing. The report is informational, not what causes the loss: Korean nationality was already gone the moment the US oath was taken, whether or not the report is ever filed. Not filing does not preserve dual status. It leaves Korean government records inconsistent with a status that has already changed, which creates its own separate problems, including using a Korean passport the person is no longer legally entitled to.
This page describes the mechanism; it does not cover Korean immigration or nationality procedure, and it is not a substitute for advice from someone qualified in Korean law on the reporting process itself.
Weighing it
The tradeoff is real and worth stating plainly rather than glossing over. US citizenship carries the right to live, work, and vote in the United States without visa dependency, US Social Security eligibility built on any US-covered work, and the ability to sponsor close family for US immigration. Against that:
- An annual US filing obligation on worldwide income for as long as the citizenship is held.
- FBAR on Korean accounts once they aggregate over $10,000.
- Form 8938 above its own thresholds.
- Continued US tax exposure even after returning permanently to Korea.
Neither side of that is a reason to file or not file; it is the actual shape of the decision.
Catching up if the US side was never filed
Someone who naturalized years ago, kept living in Korea, and never filed a US return is usually a clean fit for the Streamlined Foreign Offshore Procedures: no US abode and 330 or more full days outside the United States in at least one of the three most recently covered years qualify for the 0% offshore penalty track, so long as the underlying non-filing was non-willful, meaning a genuine gap in understanding rather than a deliberate choice to stay off the IRS's radar. The correct three years of returns and six years of FBARs still have to be filed, and any tax and interest due still has to be paid. On an accepted submission, SFOP does not assert failure-to-file, failure-to-pay, accuracy-related, information-return, or FBAR penalties for the covered years, and there is no separate offshore penalty on the foreign track.
Common questions
Do I have to give up my Korean citizenship if I naturalize as a US citizen?
Yes, automatically. Korea's Nationality Act, Article 15(1), provides that a Korean national who voluntarily acquires a foreign nationality loses Korean nationality at the moment of that acquisition. Taking the US Oath of Allegiance is a voluntary act, so Korean nationality is lost the instant the oath is completed, not on a later date.
If I don't file Korea's loss-of-nationality report, do I keep dual citizenship?
No. The report under Article 16 is informational, not what causes the loss. Korean nationality was already gone the moment the US oath was taken, whether or not the report is ever filed. Not filing just leaves Korean government records out of sync with a status that has already changed, including continued use of a Korean passport the person is no longer legally entitled to.
Does US tax residency for a Korean national start at naturalization or at the green card?
At the green card. Under IRC §7701(b)(1)(A)(i), lawful permanent resident status alone creates US tax residency from the first day of US presence as an LPR. Naturalization years later does not create new exposure; by then, the person has typically already been a full-scope US taxpayer for years.
Next step
Send the year the green card or citizenship was granted and roughly what Korean accounts, pension, or property exist. A preparer at Capital Tax Limited can confirm which years are actually open and whether the foreign Streamlined track fits, before anything is filed.
Get your situation reviewed The general family-based green card guide