Dual Citizenship and Tax Residency in Portugal: What U.S. Citizens Need to Know

For Americans living in Portugal, one of the most common sources of confusion is the distinction between dual citizenship and dual tax residency.

A U.S.-Portuguese citizen may assume that holding two passports means being tax resident in both countries. That is not necessarily the case.

Citizenship, legal residence and tax residence are separate concepts, and understanding the difference is particularly important before selling property, receiving investment income, starting a business or relocating permanently to Portugal.

This article explains how Portuguese tax residency works, why U.S. citizens generally continue to have U.S. tax obligations while living abroad, and how the Portugal–United States Double Taxation Treaty helps coordinate the two systems.

Dual citizenship does not mean dual tax residency

The starting point is simple:

Having Portuguese and U.S. citizenship does not automatically make you tax resident in both Portugal and the United States.

Citizenship identifies your legal nationality. Tax residency determines which country considers you resident for tax purposes.

Portugal determines tax residency primarily according to where you live and the circumstances of your presence in Portugal.

The United States is unusual because U.S. citizens generally remain subject to U.S. taxation on their worldwide income even when they live permanently overseas.

Consequently, a U.S. citizen living in Portugal may simultaneously have:

Portuguese citizenship;
U.S. citizenship;
Portuguese tax residency; and
continuing U.S. tax filing obligations.

That situation is common and does not, by itself, mean that something is wrong.

When are you considered tax resident in Portugal?

Portuguese tax residency is governed primarily by Article 16 of the Portuguese Personal Income Tax Code (Código do IRS — CIRS).

Under the general rules, an individual is considered Portuguese tax resident if, among other circumstances, they:

spend more than 183 days, consecutive or otherwise, in Portugal during any 12-month period beginning or ending in the relevant tax year; or
spend fewer than 183 days in Portugal but maintain a dwelling in Portugal under circumstances indicating an intention to keep and occupy it as their habitual residence.

A day of presence generally counts when it includes an overnight stay in Portugal.

This means that nationality is not the principal test.

An American citizen can be Portuguese tax resident. Equally, a Portuguese citizen living permanently abroad may cease to be Portuguese tax resident if the applicable conditions are satisfied.

What happens once you become tax resident in Portugal?

As a general rule, Portuguese tax residents are subject to Portuguese Personal Income Tax — IRS — on their worldwide income.

Depending on the taxpayer’s circumstances, this may include income such as:

employment income;
self-employment or freelance income;
pensions;
interest;
dividends;
rental income;
capital gains; and
income arising from assets located outside Portugal.

This is why determining the correct tax-residency date is particularly important.

Someone who becomes Portuguese resident partway through a year may, depending on the circumstances, fall within Portugal’s partial-year residence rules, rather than necessarily being treated as resident for the entire calendar year.

Why do U.S. citizens still file taxes in the United States?

The U.S. system works differently from most European tax systems.

A U.S. citizen generally remains subject to U.S. federal income tax rules on worldwide income regardless of where they live.

The IRS confirms that U.S. citizens living overseas are generally subject to the same basic filing requirements as citizens living in the United States.

Therefore, moving permanently to Portugal does not normally end a U.S. citizen’s federal tax filing obligations.

For example, an American who lives permanently in Portugal may still need to file a Form 1040 reporting worldwide income.

Depending on their assets and financial accounts, additional U.S. reporting obligations may also arise.

These can include reporting foreign financial accounts or specified foreign financial assets.

Does this mean paying tax twice?

Not necessarily.

This distinction is critical:

Having filing obligations in two countries is not the same as paying full tax twice on the same income.

Portugal and the United States have a Convention for the Avoidance of Double Taxation, commonly referred to as the Portugal–U.S. tax treaty.

In addition, both domestic legislation and the treaty contain mechanisms intended to reduce or eliminate juridical double taxation.

One of the most important mechanisms is the foreign tax credit.

The IRS confirms that U.S. citizens may generally be entitled to credit qualifying foreign income taxes against U.S. income tax, subject to the applicable limitations.

The Portugal–U.S. treaty also expressly provides mechanisms for relieving double taxation between the two countries.

The result is therefore not simply:

Portuguese tax + U.S. tax = double taxation.

The actual outcome depends on:

the type of income;
where the income arises;
which country has primary taxing rights;
the amount of tax paid in each country;
foreign tax credits;
treaty provisions; and
specific U.S. rules applicable to citizens abroad.

What is “dual tax residency”?

A more complicated situation can arise when the domestic laws of both countries consider the same person tax resident.

This is what is usually meant by dual tax residency.

Tax treaties include residence rules to determine which country should be regarded as the person’s treaty residence when both countries claim residence under their domestic legislation.

These are commonly known as tie-breaker rules.

Under the Portugal–U.S. treaty, the analysis generally considers factors in a defined sequence, including:

where the individual has a permanent home available;
where their personal and economic relations are closer, generally described as the centre of vital interests;
where they have their habitual abode;
nationality; and
where necessary, resolution by agreement between the competent authorities.

The analysis stops when one of the treaty tests resolves the residence question.

This means that the number of days spent in each country is important, but it is not necessarily the only relevant factor.

What is the “centre of vital interests”?

The centre of vital interests is particularly important in international relocation cases.

It looks beyond simply counting days.

Relevant factors may include:

where the taxpayer’s spouse or family lives;
location of the main home;
professional or business activities;
principal sources of income;
location of investments;
banking relationships;
social and personal relationships; and
the overall permanence of the taxpayer’s connection with each country.

There is therefore no reliable way to resolve a complex dual-residence case merely by looking at a passport or the address shown on one tax return.

The taxpayer’s actual circumstances must be examined.

A special issue for U.S. citizens: the treaty “saving clause”

For U.S. citizens, there is an additional complication that is sometimes overlooked.

U.S. tax treaties generally contain what is known as a saving clause.

The saving clause broadly preserves the United States’ right to tax its own citizens under U.S. domestic law even where they are resident in another treaty country.

The IRS explains that, because of saving clauses, U.S. citizens generally cannot simply rely on a treaty to eliminate their U.S. tax liability, although specific exceptions exist.

The Portugal–U.S. treaty contains this type of protection of U.S. taxing rights.

Portuguese tax guidance has also expressly recognised the effect of the U.S. saving clause in the treaty.

This is one reason why international tax planning for Americans living in Portugal requires more than simply deciding which country is the person’s “main” residence.

Example: U.S. citizen living permanently in Portugal

Consider an American-Portuguese dual citizen who:

owns a home in Portugal;
spends approximately 300 days per year in Portugal;
conducts their normal life from Portugal; and
only visits the United States periodically.

They are very likely to meet the Portuguese domestic criteria for tax residence.

Portugal would therefore generally expect them to report their worldwide income.

However, because they remain a U.S. citizen, they may also continue to file a U.S. federal income tax return reporting worldwide income.

The correct analysis is therefore generally not:

“Which country should I stop filing in?”

Instead, it is:

“Which country has the primary right to tax each category of income, and how is double taxation relieved?”

That distinction is fundamental.

What if the taxpayer owns a home in both Portugal and the United States?

Owning homes in both countries does not automatically create an insoluble dual-residence problem.

The analysis must establish:

whether the individual is resident under Portuguese domestic legislation;
their position under U.S. rules;
whether both countries consider them resident;
whether treaty tie-breaker rules are relevant;
where their permanent home and centre of vital interests are located; and
how each individual category of income is treated under the treaty.

The answer can therefore differ significantly between two taxpayers who both own property in Portugal and the United States.

Does tax residency affect the sale of Portuguese property?

Yes, potentially significantly.

Before selling Portuguese real estate, it is important to establish whether the owner is:

Portuguese tax resident;
Portuguese non-resident;
resident for only part of the relevant year; or
potentially subject to competing residence claims.

Residence can influence reporting obligations and the way a property disposal is analysed.

If the property is the taxpayer’s main permanent home, additional Portuguese rules may also become relevant, including potential relief where sale proceeds are reinvested in another qualifying permanent home.

For U.S. citizens, the transaction must also be reviewed from the U.S. perspective because the disposal of a Portuguese property can have reporting and tax consequences in both countries.

The two calculations will not necessarily produce the same taxable capital gain.

Should you simply “cancel” one of your tax residencies?

Usually, that is the wrong starting point.

Tax residence is not generally something that should be selected based solely on which outcome is more convenient.

It follows from facts and legal criteria.

Before changing an address with a tax authority or attempting to establish non-resident status, the taxpayer should determine:

where they actually live;
when their relocation occurred;
how many days were spent in each country;
where their habitual home is located;
where their personal and economic life is centred; and
what previous tax returns have reported.

A poorly coordinated change can create additional inconsistencies rather than resolving them.

Tax residence, immigration residence and citizenship are different

Another frequent source of confusion is the use of the word residency.

A person may be referring to entirely different concepts:

Citizenship

Nationality or citizenship, such as Portuguese or U.S. citizenship.

Immigration or legal residence

The legal right to live in a country.

Tax residence

The jurisdiction in which an individual is treated as resident for tax purposes.

Treaty residence

The country treated as the taxpayer’s residence for purposes of a particular double-tax treaty when domestic residence rules overlap.

These concepts can interact, but they are not interchangeable.

This is particularly important when assessing access to government benefits, tax incentives, healthcare arrangements, investment products or other programmes.

A programme that refuses eligibility based on “residency” may be referring to immigration residence, ordinary residence, tax residence or another specific definition.

It therefore needs to be analysed under the rules of that particular programme.

What documents should a U.S. citizen in Portugal review?

Where there is uncertainty regarding tax residence, a useful starting point is to review:

Portuguese tax-registration address;
U.S. tax returns;
Portuguese IRS returns;
dates of arrival and departure;
property ownership and rental contracts;
evidence of the main home;
employment or business location;
family circumstances;
bank and investment accounts;
foreign income;
previous certificates of tax residence; and
correspondence with Portuguese or U.S. tax authorities.

A timeline is often particularly useful.

For example:

2024 — living primarily in the United States

March 2025 — moved to Portugal

April 2025 — Portuguese home became habitual residence

2025 — continued filing Form 1040 as U.S. citizen

This allows the tax analysis to start from facts rather than assumptions.

How GoalSeek approaches Portugal–U.S. dual-residency cases

At GoalSeek, we normally approach these cases in three stages.

First, we determine the taxpayer’s Portuguese residence position under Article 16 of the CIRS, including the relevant start date.

Second, where necessary, we examine the Portugal–U.S. Double Taxation Treaty and how its residence and income-allocation rules apply.

Third, we identify the taxpayer’s Portuguese reporting obligations and coordinate them with the U.S. tax position.

For U.S. citizens, the U.S. compliance should also be reviewed by a professional familiar with U.S. international taxation because the interaction can extend beyond the annual income-tax return.

Frequently Asked Questions

Can I be a Portuguese and U.S. citizen but only tax resident in Portugal?

Yes. Citizenship and tax residency are different concepts.

However, a U.S. citizen generally continues to have U.S. federal tax filing obligations even when resident in Portugal.

If I live in Portugal, do I still have to file a U.S. tax return?

Generally, yes, provided the relevant U.S. filing thresholds and requirements are met. U.S. citizens abroad remain subject to the U.S. worldwide-income system.

Will I pay Portuguese and U.S. tax on the same income?

Potentially both countries can have taxing rights, but double-taxation mechanisms, including foreign tax credits and treaty provisions, may reduce or eliminate juridical double taxation.

The result depends on the particular type and source of income.

Is spending 183 days in Portugal the only way to become Portuguese tax resident?

No.

Even with fewer than 183 days, an individual may become Portuguese tax resident where they maintain accommodation in Portugal under circumstances indicating an intention to use it as their habitual residence.

Can the Portugal–U.S. tax treaty determine where I am resident?

The treaty contains tie-breaker mechanisms that become relevant when an individual is considered resident in both countries under their domestic rules.

However, U.S. citizens also need to consider the treaty’s saving-clause provisions.

Can I stop filing U.S. taxes because I am tax resident in Portugal?

Portuguese tax residence does not by itself terminate U.S. tax obligations arising from U.S. citizenship.

Final takeaway

For a U.S. citizen living in Portugal, dual citizenship is usually not the problem.

The important questions are:

Where are you tax resident under Portuguese law?

Do the domestic rules create competing residence claims?

How does the Portugal–U.S. tax treaty apply?

Which country has taxing rights over each category of income?

Which foreign tax credits or other double-taxation relief mechanisms are available?

Once these questions are addressed systematically, what initially appears to be a confusing “dual residency” situation is often considerably easier to manage.

If you are a U.S. citizen living in Portugal, planning a move to Portugal, or uncertain about your Portuguese tax-residency position, GoalSeek can review your circumstances, determine your Portuguese tax position and help coordinate your Portuguese obligations with your U.S. tax adviser.