What the agreement between the two countries actually does, how it works if you are self-employed in Spain, and where the 2023 update stands as of today.
This is one of the most common questions I get from Americans who have just moved to Spain: if I am paying into the Spanish system, am I also paying into the American one? The answer usually turns on a single treaty from 1988 that most people have never heard of.
That treaty is called a totalization agreement, and it does two useful things. It keeps you out of both social security systems at the same time, and it lets you combine your work history across the two countries (the part that actually gives the agreement its name) when you eventually claim a benefit.
For self-employed Americans in Spain, the first of those two things is the one that matters most, because US self-employment tax runs at 15.3% and the agreement can take it off the table entirely. That only works if you do the paperwork, though, which is where most people come unstuck.
Everything below is general information about how the agreement operates. It is not advice about your own situation, and the tax sections in particular depend on facts about your residency and your business that I do not know.
What is the US-Spain Totalization Agreement and why does it exist?
The United States has bilateral social security agreements with roughly thirty countries. The one with Spain entered into force on 1 April 1988, and the full text, along with the administrative arrangement that sits underneath it, is published by the Social Security Administration at ssa.gov.
These agreements exist because the two countries use different tests. Spain generally charges social security based on where the work is performed. The US generally taxes its own citizens on self-employment income wherever they live.
Put those rules side by side without a treaty and the same euro can be picked up twice. The agreement assigns each period of work to exactly one system, and then makes sure neither country’s minimum vesting rules quietly strand you.
From a big-picture perspective, this is a coordination document rather than a benefits document. It does not create new benefits or increase what either country pays you.
The two problems it solves: double contributions and benefit gaps
The first problem is double contributions. Without the agreement, the same earnings could be subject to Spanish social security and to US Social Security or self-employment tax, with no credit in either direction.
That is not a rounding error. Spanish contributions are substantial on their own, and a US layer on top would be a second charge on money already taxed once for the same purpose.
The second problem is quieter and shows up decades later. Each system requires a minimum contribution history before it pays anything, and a career split across two countries can leave you short in both.
Someone with eight years in the US and fifteen in Spain has a real working life behind them. Read under each country’s rules in isolation, though, that record could produce nothing from either system. The totalization provisions are what prevent that outcome.
How it works for US employees sent to Spain by a US employer
The core rule for employees is in Article 5(1) of the agreement, and it is usually called the detached worker rule. If a US employer sends an employee to work temporarily in Spain, the employee stays covered by the US system rather than switching to the Spanish one.
The word “temporarily” has a specific meaning here. The article applies where the work “is not expected to exceed five years,” measured by the expectation at the outset rather than by what happens later.
If unforeseen circumstances stretch the assignment past that point, coverage may continue “for a new period of not more than one year, provided that the Competent Authority of the other Contracting State has given its consent.” The rule in force today is therefore five years, extendable by one.
That extension is worth reading slowly. The sixth year is not automatic, and it is not something the employee can elect. It is a request that the other country has to approve.
| Your Situation | Which System Generally Covers You |
|---|---|
| Sent by a US employer, assignment under five years | United States |
| Hired locally by a Spanish employer | Spain |
| Self-employed and resident in Spain | Spain |
The middle row catches more people than the first one does. If you took a job with a Spanish company, or your US employer moved you onto a Spanish payroll (or onto a local Spanish entity), you are almost certainly in the Spanish system. The detached worker rule is narrow, and it turns on the assignment rather than on your passport.
How it works for self-employed Americans in Spain
Here is where the agreement earns its keep for a large share of my practice. A US citizen who is selfemployed, resident in Spain, and covered by Spanish social security, and who holds a certificate of coverage, is exempt from US self-employment tax on that same self-employment income. The SSA’s own pamphlet on the Spain agreement, published at ssa.gov, sets out the mechanism.
US self-employment tax (the SECA tax, which funds Social Security and Medicare for people with no employer withholding) is levied at 15.3%. It applies to US citizens on self-employment income wherever they live, and it is not reduced by the foreign earned income exclusion or by foreign tax credits. That surprises people who assumed the exclusion covered everything.
As a hypothetical illustration using round numbers, not a real case: an American freelancer resident in Valencia with $60,000 of net self-employment income would face US self-employment tax of roughly $8,000 to $9,000 if no exemption applied. If that same person is covered by Spanish social security and holds a certificate of coverage, the agreement takes the income out of the US self-employment tax base. What any particular person owes depends on their own facts and how the business is structured.
The exemption is not automatic, and you do not claim it by leaving the income off the return. You claim it by filing and attaching documentation that references the agreement and the certificate of coverage issued by the Spanish authorities. I would leave the exact mechanics to whoever prepares the return, because the presentation matters and it changes over time.
The certificate is the whole ballgame
The self-employment tax exemption depends on being able to show that Spain is covering you. Without a certificate of coverage in hand, you have a position you believe in and no document to support it. Request the certificate when you register, not the week the return is due.
The autónomo side of the equation
Meanwhile, on the Spanish side, a self-employed American in Spain registers as autónomo and pays the monthly cuota. Spain moved the autónomo system to an income-based contribution scale, so the amount owed is tied to declared earnings rather than to a flat figure.
That matters for planning, because your contributions now move with your income and the base you declare feeds into what Spain eventually pays you. Keep in mind that the point of the agreement is not that you pay nothing. It is that you pay into one system rather than two.
The 2023 agreement: signed, not yet in force, and what we know so far
A new social security agreement between the United States and Spain was signed on 8 April 2023. As of August 2026, it has not entered into force.
I want to be careful here, because this is an area where confident claims have traveled further than the facts behind them. The full text has not been published by the SSA, and the SSA’s own list of agreements in force still shows Spain with the 1988 date only.
Entry into force follows a Congressional review period under the fast-track process in the Social Security Amendments Act. Prior US totalization agreements have generally taken a couple of years from signature to entry into force, though this one has now run considerably longer than that.
Several law firm blogs have written that the new agreement extends the detached worker period from five years to seven. I have seen that figure circulating widely. There is no primary source for it that I have been able to find, and until the SSA publishes the text, nobody outside the negotiating rooms actually knows.
So my position is straightforward. The only rule anyone should plan around today is the five-plus-one rule that is in force. If you are structuring an assignment on the assumption of a seven-year window, you are relying on a number neither government has confirmed.
When the text is published, the planning conversation may change. Until then, I would rather tell you what is not yet known than repeat a figure because it appeared in enough places to sound settled.
How to get a certificate of coverage, and why you need one
A certificate of coverage is the document that proves which system you belong to. The rule of thumb is simple: you request it from the system that is covering you (not from the one you are trying to stay out of).
If Spain covers you, the certificate comes from the Tesorería General de la Seguridad Social (TGSS). If the US covers you, because you are a detached worker on a US assignment, the certificate comes from the SSA.
I am not going to list Spanish form numbers here, because the TGSS procedure and its online routes change. Confirm the current steps directly with the TGSS or through your gestor rather than following a stale instruction from an article. The shape of the process does not change: an application to the covering authority, a certificate issued for a defined period, and a copy retained by you.
Two practical notes. Certificates cover a defined period and they expire, so an assignment or a self-employment arrangement that runs long needs a renewal. Also, keep the certificate with your tax records rather than in an email folder, because it may be requested years after it was issued.
Combining work credits across both countries to qualify for benefits
Totalization means adding periods together to reach a qualifying threshold. If you do not have enough coverage in one country’s system to qualify on your own, the agreement lets you count your periods in the other country toward that country’s minimum.
The US minimum for a retirement benefit is 40 credits, which is roughly ten years of covered work. Someone with seven years of US coverage and a long Spanish career can use the Spanish periods to get over the US line (and the same logic runs in the other direction for Spanish benefits).
Here is the part people misunderstand, so let me explain. Combining credits qualifies you for a benefit. It does not enlarge either benefit beyond what your own contributions actually earned.
Each country then pays a partial benefit, calculated only on the periods you actually worked under that country’s system. You are not paid twice for the same years, and the Spanish periods that helped you qualify in the US do not increase the US payment. Two partial benefits from two systems is the normal outcome, and it beats one benefit and one forfeited record.
The WEP repeal and what it means for Americans with both US and Spanish benefits
This is the piece of the picture that changed most recently, and it is good news for people with split careers. The Social Security Fairness Act was signed into law on 5 January 2025 and repealed both the Windfall Elimination Provision (WEP) and the Government Pension Offset (GPO). The SSA’s page on the law is at ssa.gov.
To make this as clear as possible: WEP used to reduce a person’s US Social Security benefit when they also received a pension from work not covered by US Social Security. A Spanish pension is exactly that kind of pension. So an American with part of a career in Spain and part in the US could see the US benefit cut by a formula most people found impossible to follow.
That reduction is gone. Benefits are payable without the WEP or GPO reduction for months after December 2023, which means January 2024 and later. The SSA began issuing retroactive payments in February 2025 and has reported that it substantially completed the retroactive processing during 2025.
If your US benefit was reduced by WEP before 2024 and you have not looked at your record since, that is worth checking. I am not going to tell you what the change is worth in dollars, because it depends on your own earnings record. What I will say is that the reduction no longer applies, and that SSA has been adjusting records without requiring people to apply.
Three things to check this month
One, do you hold a current certificate of coverage from whichever system covers you? Two, if you are self-employed, has the agreement exemption been reflected on your US returns? Three, if WEP ever reduced your benefit, has SSA updated your record?
Work with a cross-border adviser to coordinate both systems
Most of what goes wrong here is not a hard technical question. It is a coordination problem. Registering the autónomo and handling the cuota sits on the Spanish side. Filing the 1040 and the foreign forms sits on the US side, and that is plenty of work on its own. The certificate of coverage sits between the two, which is exactly why it is the thing that gets missed, and the self-employment tax then gets paid year after year when it did not have to be.
That is the specific gap I work in. Cross Border Wealth Advisors is a fee-only registered investment adviser, and I hold both the CFP® and the Enrolled Agent credential. The tax return and the financial plan therefore get decided in the same conversation instead of being handed between two firms.
On this topic the work is concrete: confirming which system covers you, making sure a certificate of coverage exists and is current, checking that your US return claims the exemption correctly if it applies, projecting both benefit streams so you can see the combined picture, and reviewing your record if WEP ever reduced your US benefit. None of that is exotic. It just has to be done by someone reading both rulebooks at once.
If you are living in Spain, or planning a move, and you are not certain which system you belong to, that conversation is better had before the next filing season than after. You can schedule an introductory conversation at www.cbwealthadvisors.com or email me at info@cbwealthadvisors.com.
Everything above is general information about how the US-Spain agreement works, not advice about your particular circumstances. Your residency, your business structure, and your work history in each country all change the answer, and I would want to see those facts first.
Sources
Primary sources are cited first. Links are provided for the reader’s convenience and are current as of the publication date.
- SSA, U.S.-Spanish Social Security Agreement (full text and Administrative Arrangement)
- SSA, Totalization Agreement with Spain (pamphlet)
- SSA, Social Security Fairness Act (WEP and GPO repeal)
- Bloomberg Tax, Expatriates, Cross-Border Workers Must Plan for Social Security
Important disclosures
This article is general educational information published by Cross Border Wealth Advisors, a company of Gersten Financial Planning Inc. an investment adviser registered with the State of California (CRD 309890). Nothing in it is investment advice, tax advice, legal advice, or immigration advice, and nothing in it is an offer or solicitation to buy or sell any security.
Tax and reporting rules in the United States and in Spain change, and their application depends entirely on your own facts. Figures, thresholds, rates and filing dates are stated as of the publication date shown above and may have changed since. Before acting on anything described here, consult a qualified professional about your own situation. Where this article says a point is unsettled or unconfirmed, that statement is deliberate and should be treated as a reason to seek advice rather than as a conclusion.
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