About Taxbordr: founder-led US-Portugal advisory
Taxbordr is a Portugal-registered cross-border tax practice run by Telmo Ramos, member of the Ordem dos Economistas (Cédula nº 16379), based in Lisbon, with prior Big Four experience at KPMG Luxembourg and EY Lisbon. We work with US citizens, Green Card holders, accidental Americans (born in the US, raised abroad, never lived there), and US CPAs whose clients have moved or are about to move to Portugal. Typical engagements are a Tax Position Review pre-move (sequencing the move date, IRA / 401(k) / Roth conversions, and the IFICI question), an IFICI eligibility decision, or coordinated annual filing once Portuguese residency is in place. We do not file Form 1040, FBAR (FinCEN 114), or Form 8938 with the US side. Your US CPA does. We own the Portuguese return, the AT correspondence, and the Modelo 3 Anexo J position.
The 1994 US-Portugal Tax Treaty
The 1994 US-PT Tax Treaty (signed 6 September 1994, in force 1 January 1996) is still the operative instrument. Three articles are central for individuals. Article 16 (Dependent Personal Services) allocates employment income; cross-border employees need a careful 183-day count. Article 20 (Pensions, Social Security, Annuities, Alimony) governs private pensions and Social Security. Article 21 (Government Service) governs pensions and salaries paid by US Government bodies (federal civilian, military, certain teacher schemes funded from US public funds). The Treaty also contains a Saving Clause (Protocol para 1) that preserves the United States' right to tax its citizens and Green Card holders on worldwide income notwithstanding most treaty articles, with named exceptions. The Saving Clause is why a US citizen resident in Portugal still files Form 1040 every year.
US Social Security: Article 20 and credit mechanics
Article 20 is a high-risk filing point. The United States has taxing rights over US Social Security, and Portuguese treatment can depend on treaty residence, citizenship, and whether foreign-tax-credit relief is required. The IRS Chief Counsel information letter GENIN-137208-15 states that where a recipient is a Portuguese resident and a US citizen, both countries may tax the benefits, with the United States retaining the primary right and Portugal relieving double taxation through a credit or deduction mechanism. The practical filing step is to document the Article 20 position before the Portuguese return is prepared.
Worldwide income, Form 1040, and the Foreign Tax Credit
US citizens and Green Card holders file Form 1040 on worldwide income regardless of where they live. The two main mitigations against double taxation are the Foreign Earned Income Exclusion (FEIE) on Form 2555 and the Foreign Tax Credit (FTC) on Form 1116. FEIE excludes the first USD 130,000 (2025) / USD 132,900 (2026, per IRS Rev. Proc. 2025-32) of foreign earned income, subject to the bona fide residence or physical-presence tests. FTC is generally more favourable for clients with high-tax foreign source income (Portugal at progressive IRS rates often exceeds the FEIE ceiling). The choice is per-source-of-income and per-year. Sequencing matters: once you elect FEIE and revoke, you cannot re-elect for five years without IRS consent. Schedule B (interest and dividends), Schedule D (capital gains), and Form 8938 (specified foreign financial assets, if thresholds are met) are the recurring items.
FBAR (FinCEN 114) and Form 8938: not the same
FBAR (FinCEN Form 114) is a Treasury / FinCEN report, not an IRS form. It is required if the aggregate maximum balance across all foreign financial accounts exceeded USD 10,000 at any time during the calendar year. It is filed separately from Form 1040 with FinCEN, due 15 April with automatic extension to 15 October. Form 8938 is the IRS specified-foreign-financial-asset report under FATCA, filed with Form 1040. The thresholds are higher than FBAR and depend on filing status and residence: for unmarried taxpayers living abroad, the year-end threshold is USD 200,000 or USD 300,000 at any time; married filing jointly abroad is USD 400,000 / USD 600,000. Reasonable cause defences differ between the two regimes. Many Portuguese arrivals trigger FBAR almost immediately (a typical Caixa Geral or Millennium account plus a brokerage account passes USD 10,000 quickly) and trigger 8938 with a delay tied to balance accumulation.
FEIE vs FTC: how to choose
Two simple decision points. (1) If your foreign earned income is below the FEIE ceiling and you have little or no other US-taxable income, FEIE on Form 2555 produces a clean low-or-zero US tax outcome but generates no FTC carryforward. (2) If your foreign earned income exceeds the FEIE ceiling, or you have significant US-source income, or you want to build FTC carryforward for future years (high-PT-tax / low-US-tax differential), FTC on Form 1116 is usually the better instrument. The IFICI question changes the calculation: under IFICI, employment income (Cat A) is taxed at 20% in Portugal; if you also use FEIE, you waste the IFICI 20% rate inside the FEIE ceiling. Often the right answer for an IFICI-eligible US arrival is FTC on Form 1116, not FEIE. We model both per case before the move.
US-PT Totalization Agreement (1988)
The US-Portugal Totalization Agreement (effective 1 August 1989) prevents double Social Security taxation for posted workers. Form USA/PT 1 (Certificate of Coverage) issued by the SSA exempts a US-employer-posted worker from Portuguese Segurança Social for up to 5 years, extendable by mutual agreement (typically up to 1 additional year). Self-employed Americans in Portugal generally fall under Portuguese Segurança Social from arrival; the Agreement totalizes credits across the two systems for benefit-eligibility purposes. Posted workers from US employers who skip the Form USA/PT 1 step end up double-paying SS contributions for the first months and then dealing with refund mechanics; the form needs to be in place before the assignment starts.
Single-member US LLC: the Portuguese classification question
A US single-member LLC is, by US default, a disregarded entity for federal tax purposes. The owner reports the LLC's income on Schedule C of Form 1040 as if the LLC did not exist. Portugal does not automatically respect the disregarded-entity classification. Portuguese treatment depends on whether the LLC is classified as transparent or opaque under Portuguese tax principles applied to the legal form (membership structure, governance, profit-distribution mechanics). Most Portuguese SME tax practice treats a US LLC as either (a) opaque (a foreign company; profits taxed only when distributed; gain a corporate veil concern) or (b) transparent (look-through; profits taxed annually on the member). The classification has dramatic consequences for IFICI eligibility, autonomous taxation, and timing. This is one of the highest-value items on a US move file: it is decided at the position-memo stage, before the LLC is set up or the first invoice is issued.
Roth IRA, Traditional IRA, and 401(k) in Portugal
The US tax-favoured status of these accounts is a US construct. Portugal looks through the wrapper. The distinction matters at distribution. Traditional IRA / 401(k): distributions are Cat H pensions in Portugal, taxable in the residence state under Treaty Article 20 (private pensions). US withholding generally not applied if the SSA-1099 / 1099-R reporting is correct; if applied, recoverable by FTC on Modelo 3. Roth IRA / Roth 401(k): the "tax-free in the US" status does not translate to tax-free in Portugal in all cases. Portuguese practice has not produced a single uniform answer on Roth distributions; the analysis hinges on whether the Roth payment is treated under Article 20 as a pension (residence-state taxation in Portugal) or as a capital distribution that escapes Article 20 framing. This is a per-case position memo, not a generic FAQ. The brokerage account holding the Roth (BAML, Schwab, Vanguard, Fidelity) typically does not change the Portuguese answer.
Common US move mistakes we re-litigate
"US Social Security is a simple no-tax line in Portugal." Wrong. Article 20 and credit mechanics need to be documented, especially where the recipient is also a US citizen.
Filing FEIE on Form 2555 with an IFICI 20% rate already in place. The 20% IFICI rate is wasted inside the FEIE ceiling. FTC is usually the right instrument.
Forgetting Form 1099-DA: mandatory broker reporting of digital-asset proceeds for transactions on or after 1 January 2025; basis reporting from 2026.
PFIC trap on European-domiciled UCITS funds (anything not a US-registered mutual fund). Form 8621, mark-to-market or QEF election. Portuguese banks default to UCITS funds; the US side punishes them.
US single-member LLC set up before a Portuguese position memo. Transparent-vs-opaque classification not pre-resolved.
Confusing FBAR with Form 8938. Different regimes, different thresholds, different penalties.
Skipping Form USA/PT 1 on a US-employer-posted assignment to Portugal and double-paying SS for the first months.
Frequently Asked Questions
Do US citizens pay tax in Portugal and the US?
US citizens and Green Card holders file Form 1040 on worldwide income wherever they live. Once Portuguese tax residency is in place, the same income is in scope in Portugal. Double taxation is mitigated by the Foreign Tax Credit (Form 1116), the Foreign Earned Income Exclusion (Form 2555), and the 1994 US-PT Tax Treaty.
Can Portugal tax my US Social Security?
Do not file this as a simple no-tax line without a treaty check. The United States has taxing rights under Article 20, and Portugal-side reporting or relief can depend on treaty residence, citizenship, and credit mechanics.
When do I file FBAR?
When aggregate maximum balances across all foreign financial accounts exceeded USD 10,000 at any time during the calendar year. FBAR (FinCEN 114) is filed with FinCEN separately from Form 1040, due 15 April with automatic extension to 15 October.
When do I file Form 8938?
When you meet the FATCA thresholds for specified foreign financial assets. For an unmarried taxpayer living abroad, the year-end threshold is USD 200,000 or USD 300,000 at any time. Married filing jointly abroad: USD 400,000 / USD 600,000. Filed with Form 1040.
FEIE or FTC?
FEIE (Form 2555) excludes the first USD 130,000 (2025) / USD 132,900 (2026) of foreign earned income but generates no carryforward. FTC (Form 1116) credits the foreign tax paid against US tax and builds carryforward. For high-PT-tax / IFICI-rate situations, FTC is usually the better instrument. Election is per year.
Can a US citizen claim IFICI?
Yes. IFICI eligibility (EBF art 58-A) does not depend on nationality. The conditions are five-year non-residence in Portugal and a qualifying activity. The Saving Clause means the IFICI 20% rate on Cat A income still leaves the income subject to US tax on Form 1040; the Foreign Tax Credit on Form 1116 limits the US tax to the FTC ceiling.
How is my Roth IRA taxed in Portugal?
Portuguese practice has not produced a single uniform position on Roth distributions. The "tax-free in the US" status does not automatically translate. The analysis depends on whether the Roth payment is treated as a pension under Article 20 (residence-state taxation in Portugal) or as a capital distribution that escapes Article 20 framing. This is a per-case position memo.
Does my US single-member LLC stay disregarded in Portugal?
Not automatically. Portugal classifies the LLC under Portuguese principles applied to the legal form. The LLC may be treated as opaque (foreign company) or transparent (look-through). The classification has IFICI, autonomous-taxation, and timing consequences. Resolve before invoicing, not after.