Dual citizenship in Spain for Americans: what the oath really changes

Spain and the United States have no dual nationality treaty, and the United States is not on Spain’s exempt list. So an American who becomes Spanish is asked at the ceremony to renounce US citizenship — and that renunciation has no effect under US law, because Washington only accepts one made in person before a consular officer abroad. The practical result is two passports, and a set of duties that comes with each.

What Spain actually asks for

Article 23 of the Civil Code makes three things conditions for acquiring Spanish nationality by residence: an oath of loyalty to the King and obedience to the Constitution, a declaration renouncing the previous nationality, and registration in the Civil Registry. The renunciation requirement is waived only for nationals of Ibero-American countries, Andorra, the Philippines, Equatorial Guinea and Portugal, and for Sephardic Jews of Spanish origin. The United States is not on that list.

So the declaration is made, the registrar records it, and Spain considers the condition met. Spain does not ask Washington to confirm anything, does not forward the declaration, and does not check later whether the US passport still exists.

What the United States requires to lose citizenship

US nationality ends only through one of the expatriating acts in section 349(a) of the Immigration and Nationality Act, and only when the act is voluntary and performed with the intention of giving up citizenship. In practice that means a formal renunciation before a US consular officer outside the United States, with an oath, an interview, a fee and a Certificate of Loss of Nationality. The Department of State also applies a presumption that a citizen who obtains another nationality or swears allegiance to another state intends to keep US citizenship.

A declaration made in a Spanish civil registry is none of those things. It is a statement to Spanish authorities, in Spain, in a Spanish procedure. For the United States you remain a citizen with every obligation attached — filing included.

Routes to Spanish nationality for an American

Two points that catch Americans out. First, the ten years are counted as legal residence, so the status you hold matters more than the years you have spent in the country: study stays do not count, while residence permits do — see the routes to a Spanish residence permit, the digital nomad permit, the non-lucrative permit and the research residence permit. Second, dual Spanish–American citizens by descent are a different story entirely: a child born to a Spanish parent is Spanish from birth and never has to renounce anything.

The real risk comes after the ceremony

Article 25 of the Civil Code lets Spain strip nationality from someone who acquired it — not from those Spanish by origin — if for three years they use exclusively the nationality they declared they were renouncing. Article 24 adds the mirror rule for Spaniards who take another nationality: they lose Spanish nationality unless they declare, within three years, that they wish to keep it.

For an American with a Spanish passport this is the practical trap. Renewing only the US passport, entering and leaving Spain on it, dealing with Spanish authorities as an American — each of those is evidence of exclusive use. The remedy is unglamorous and effective: hold a valid Spanish DNI and passport, use them in Spain and at Spanish borders, and keep the US passport for what US law requires.

Because US law does require it: US citizens must enter and leave the United States on a US passport. Two valid passports is not a contradiction here — it is the correct arrangement. You show the Spanish one to Spain, the American one to the United States.

What citizenship does not change: taxes

The United States taxes its citizens on worldwide income wherever they live, and a Spanish passport does not alter that. An American living in Spain files in both countries and uses the treaty and credits to avoid paying twice.

• The tax treaty. The 1990 convention between the United States and Spain, as amended by the 2013 protocol, sets which country taxes what and how relief is given.
• Social security. The totalization agreement has been in force since 1 April 1988: you contribute to one system rather than both, and periods in the two countries can be combined when a pension is claimed.
• US reporting. Foreign accounts are reported on the FBAR once the combined balance passes the threshold, and specified foreign assets on Form 8938. Neither is a tax; both carry penalties when skipped.
• Spanish reporting. As a Spanish tax resident you may also owe the annual declaration of assets abroad — that is Modelo 720 and 721, and for an American it usually means declaring the very accounts already reported to the IRS.
• The special regime. the Beckham law can cut Spanish tax sharply in the first years after a move, but it is aimed at new arrivals with a Spanish employment link, and it does nothing about US filing.

The sequencing matters more than the forms. Decisions made in the year before the move — selling a company, realising gains, rolling over a retirement account — are usually worth more than anything done afterwards, and they are decided by residence, not by passport.

Living with two passports

• Entering the United States: on the US passport, always.
• Entering Spain and the rest of the EU: on the Spanish passport or DNI; that is also what keeps Article 25 at bay.
• Consular help: inside Spain the United States cannot assist you as a foreign national, because Spain treats you as Spanish. That is the ordinary rule of dual nationality, not a Spanish peculiarity.
• Military and civic duties: each country applies its own to its own citizens.
• Renouncing for real: if you decide to end US citizenship, it happens at a US consulate, with a fee and an interview, and it has tax consequences of its own, including a possible exit tax. It is a tax decision as much as an identity one.

How the same questions play out for other nationalities is covered in dual citizenship in Spain for Russians, and the citizenship procedure itself — documents, the exam, the oath, timelines — in Spanish citizenship. If you are still at the stage of choosing a route and a tax year for the move, that is worth mapping before you file anything: with US citizenship in the picture, the order of steps decides how much of the move you keep. See also moving to Spain from the US and permanent residence.

Frequently asked questions

Does Spain allow dual citizenship with the United States?

There is no treaty between the two countries, and the United States is not among the states whose nationals are exempt from renouncing. Spain therefore asks for a declaration of renunciation at the oath. The United States does not treat that declaration as a loss of citizenship, so in practice Americans keep both nationalities.

Will I lose my US citizenship if I become Spanish?

Not by becoming Spanish. US citizenship ends only through an expatriating act performed voluntarily and with the intention to relinquish, normally a formal renunciation before a US consular officer abroad. The Department of State presumes that someone acquiring another nationality intends to keep US citizenship.

How long must an American live in Spain before applying?

Ten years of legal, continuous residence immediately before the application, unless a shorter period applies: one year for a spouse of a Spanish national or for someone born in Spain, five years for refugees. The two-year rule for Ibero-American nationals does not extend to US citizens.

Can Spain take back the nationality it granted?

Yes. Article 25 of the Civil Code allows it when a person who acquired Spanish nationality uses exclusively the nationality they renounced for three years. Holding a valid Spanish passport and DNI and using them in Spain is the simple way to avoid the question.

Which passport do I use at the border?

The US passport to enter and leave the United States, as US law requires, and the Spanish passport or DNI for Spain and the rest of the European Union. Carrying both is normal for dual nationals.

Do I still file US taxes after getting a Spanish passport?

Yes. The United States taxes citizens on worldwide income regardless of where they live. The 1990 treaty as amended in 2013 and the foreign tax credit prevent double taxation, and the totalization agreement of 1988 keeps you out of two social security systems at once, but the filing obligation itself remains.

Is the Democratic Memory route still open for grandchildren of Spaniards?

No. The window under additional provision 8 of Law 20/2022 closed on 22 October 2025 after a single one-year extension, and applications are no longer accepted at consulates or civil registries. Descendants now have to look at the ordinary routes.

Sources

• Spanish Civil Code, Articles 17 to 26 (consolidated text, BOE)
• U.S. Department of State: dual nationality
• U.S. Social Security Administration: totalization agreement with Spain
• IRS: United States — Spain tax treaty documents
• Ley 20/2022 on Democratic Memory, additional provision 8