What a totalization agreement is
International social security agreements, which the US calls totalization agreements, have 2 purposes according to the Social Security Administration: they end dual social security taxation when someone from one country works in the other, and they fill gaps in benefit protection for people who split a career between the 2 countries.
They generally do not let you pick a system. Each agreement applies fixed rules rather than a choice of where to contribute (SSA), and only the 2 countries' authorities can agree on an exception in unusual cases, such as an assignment that runs a few months past its limit. Italy's is the one agreement with a choice: Italian and dual US-Italian nationals who would be covered by both systems must elect one within 3 months after the month the work begins (SSA POMS RS 02001.070).
They also leave income tax alone. An agreement covers social security taxes only, so your salary, your dividends and your crypto gains are still taxed where you are resident, with the income tax treaty between the 2 countries settling any overlap. Your income tax as a digital nomad and your contributions can therefore be due in 2 different countries.
Totalization agreement or tax treaty?
Right
A US engineer is sent to her employer's London office for 3 years. The US-UK totalization agreement keeps her in US Social Security, and the US-UK income tax treaty plus her residence decide who taxes her salary.
Wrong
The same engineer reads the totalization agreement as settling her income tax too and files nothing in the UK. The agreement exempts her from UK National Insurance only; UK income tax on her London work is a separate question.
Countries with a US totalization agreement
The US has agreements in force with 31 countries, listed here with the date each original agreement entered into force (SSA, read October 12, 2026). 24 are in Europe; the other 7 are Australia, Brazil, Canada, Chile, Japan, South Korea and Uruguay.
US totalization agreements in force, October 2026
| Country | In force since |
|---|---|
| Italy | November 1, 1978 |
| Germany | December 1, 1979 |
| Switzerland | November 1, 1980 |
| Belgium | July 1, 1984 |
| Norway | July 1, 1984 |
| Canada | August 1, 1984 |
| United Kingdom | January 1, 1985 |
| Sweden | January 1, 1987 |
| Spain | April 1, 1988 |
| France | July 1, 1988 |
| Portugal | August 1, 1989 |
| Netherlands | November 1, 1990 |
| Austria | November 1, 1991 |
| Finland | November 1, 1992 |
| Ireland | September 1, 1993 |
| Luxembourg | November 1, 1993 |
| Greece | September 1, 1994 |
| South Korea | April 1, 2001 |
| Chile | December 1, 2001 |
| Australia | October 1, 2002 |
| Japan | October 1, 2005 |
| Denmark | October 1, 2008 |
| Czech Republic | January 1, 2009 |
| Poland | March 1, 2009 |
| Slovak Republic | May 1, 2014 |
| Hungary | September 1, 2016 |
| Brazil | October 1, 2018 |
| Uruguay | November 1, 2018 |
| Slovenia | February 1, 2019 |
| Iceland | March 1, 2019 |
| Romania | September 1, 2026 |
Most nomad bases have no US agreement
Mexico, Costa Rica, Thailand, Indonesia, the UAE and Georgia are not on the list, so a self-employed American living in any of them stays liable for US self-employment tax and has no certificate to show. Settling in a base that charges no local contributions does not remove the US bill.
How the agreements decide which country covers you
Employees: where you work, unless you are sent for 5 years or less
The basic rule in every US agreement looks at where the employee works: someone who would otherwise be covered by both systems is covered only by the country where the work is done (SSA).
Each agreement except Italy's adds an exception for temporary assignments. An employee transferred by the same employer to work in the other country stays covered only by the sending country if the assignment is expected to last 5 years or less, a limit the SSA describes as substantially longer than in other countries' agreements. Inside the EU an employer can post you to another member state for up to 24 months, covered by an A1 certificate the employer applies for before the posting starts (European Commission).
The exception also covers transfers to a foreign affiliate rather than a branch, but only if the American employer has an agreement with the Treasury under section 3121(l) of the Internal Revenue Code covering that affiliate (SSA).
The self-employed: residence, place of work or nationality
US coverage reaches self-employed US citizens and residents wherever they work (SSA), so abroad they are covered twice wherever the host country also charges the self-employed, unless an agreement applies. The agreements fix it in different ways, and the SSA states each country's rule; these 11 show the range:
How 11 US agreements assign a self-employed person
| Agreement with | Self-employed person covered by |
|---|---|
| United Kingdom, Ireland, Portugal, Spain, Switzerland | The country of residence |
| Brazil, Czech Republic, Hungary, Uruguay | The country where you work, if you work only there; a business moved for 5 years or fewer stays in the original system |
| Romania | The country where you work; a business moved for less than 5 years stays in the original system if the home country decides the work is similar (SSA) |
| Italy | Nationality: a US national who is not also Italian stays in US Social Security only; Italian and dual nationals elect one system |
Where no agreement applies, US self-employment tax abroad stays due on top of any local contributions, and the foreign earned income exclusion does not reduce it (IRS).
Will you pay more or less than US self-employment tax?
Being assigned to the other country's system can cost more or less than staying in the US system. A US freelancer paying Hungary's social security and social contribution tax or Portugal's freelancer social security gives the local system more than US self-employment tax would take, and one paying UK Class 4 National Insurance or Irish PRSI pays far less.
Source: Nomad Tax Index country data The US figure is 15.3% on 92.35% of the $85,000 profit, below the $184,500 wage base. Hungary includes its social contribution tax, Czechia and Romania include health insurance, and Switzerland includes administration costs. Brazil's INSS is capped at the 2026 ceiling of BRL 20,341 (about $3,910) a year; Uruguay's is the fixed lowest-category BPS contribution of UYU 105,996 (about $2,630) a year. Italy is left out because its agreement keeps a US national who is not also Italian in US coverage.
Show the numbers
| Share of profit | |
|---|---|
| Hungary | 18.2% |
| Portugal | 17.6% |
| US self-employment tax | 14.1% |
| Romania | 13.6% |
| Czechia | 11.8% |
| Switzerland | 10.5% |
| Spain | 8.8% |
| Brazil | 4.6% |
| Ireland | 4.2% |
| United Kingdom | 4% |
| Uruguay | 3.1% |
How to get a certificate of coverage
An exemption under an agreement is not automatic. You prove it with a certificate of coverage from the country that keeps covering you: a US worker on assignment in the UK needs a certificate from the SSA to show the UK authorities, and a UK-based employee working in the US needs one from the UK (SSA).
Employers request certificates for the employees they transfer abroad; self-employed people request their own. Employers and performers or entertainers can use the SSA's online Certificate of Coverage service or send the request by mail or fax, while other self-employed people must request by mail or fax (SSA POMS RS 02001.005).
When the other country covers you, the certificate comes from its authority. A self-employed US citizen covered abroad attaches a copy of that foreign certificate to the US tax return every year as proof of the exemption from self-employment tax, under Revenue Procedure 84-54 (SSA).
David's note
I would request the certificate of coverage before the first invoice or the first paycheck abroad, not when a contribution demand arrives. With the certificate in hand from day 1, nothing is withheld in the wrong country and there is nothing to reclaim later.
What a certificate of coverage request needs
- The employer's name in the US and in the other country, for an employee.
- The worker's full name, date and place of birth, and citizenship.
- The worker's US and foreign Social Security numbers.
- The start and end dates of the assignment; an employee's exemption generally covers up to 5 years.
- For the self-employed, the country of residence and the nature of the work.
- Under the agreements with France and Japan, whether the worker and any family members have health insurance.
Totalization benefits: adding up credits for a pension
The second half of each agreement deals with pensions. A worker generally needs 40 quarters of coverage for a US retirement benefit, and someone who split a career between 2 countries can fall short in both (SSA).
Under an agreement the SSA counts the other country's coverage toward that test, but only if you have at least 6 quarters of US coverage, and then pays a partial benefit in proportion to the share of your career completed in the US. The other country does the same with your US periods, subject to its own minimum (SSA).
You do not need to do anything about benefits until you claim, and a claim under an agreement can be filed at any Social Security office in the US or in the other country. Without an agreement, the contributions you paid abroad for a few years may never qualify for a benefit there.
Social security agreements between other countries
The EU's coordination rules apply across the EU, Iceland, Liechtenstein, Norway and Switzerland and keep you under only 1 country's legislation at a time (European Commission), with the A1 as their certificate of coverage (European Commission). The UK's list of agreement countries outside the EU, the EEA and Switzerland includes Barbados, Canada, India, Israel, Japan, Mauritius, the Philippines, South Korea, Turkey and the US (HMRC).
Where no agreement links your home country and the country you work from, social security for digital nomads comes down to each country's own law, and both can charge on the same income.
