Self-employed in Spain as a UK or EU national: tax residence, autónomo and Social Security

Three separate questions, in this order

Living in Valencia with a Spanish residence document raises three questions that are often mixed up: where you are tax resident, which country’s Social Security legislation applies, and what you must register in Spain. They are answered under different rules. A residence document, a NIE or a Spanish bank account does not, by itself, answer any of them.

Tax residence: more than 183 days, or your centre of interests

You are resident in Spain for Personal Income Tax if you spend more than 183 days here in the calendar year. Sporadic absences count towards that period unless you prove tax residence in another country. You are also resident if the main centre or base of your activities or economic interests is in Spain, directly or indirectly. And residence is presumed, unless proven otherwise, if your spouse, not legally separated, and your dependent minor children habitually live in Spain (Personal Income Tax Act, article 9.1).

A resident is taxed on worldwide income, wherever it was obtained and whoever pays it (article 2), and the tax period is the calendar year (article 12.1). Fees invoiced to UK or other foreign clients are therefore part of your Spanish return if you are resident. Our guide to tax residence when moving to Spain covers the year of arrival and credit for foreign tax.

If the UK also treats you as resident: the treaty tie-breaker

Where a person is resident of both Spain and the United Kingdom under each country’s law, the Spain–UK tax treaty resolves it in a fixed order (article 4.2): first, where you have a permanent home available; if you have one in both, where your personal and economic relations are closer (centre of vital interests); then where you habitually live; then nationality; and, failing that, the two tax authorities settle it by mutual agreement. Each step applies only if the previous one gives no answer.

The order matters in practice. Keeping a house in the UK while renting in Valencia sends the analysis to your centre of vital interests, where family, work and assets are weighed together. For business profits, the treaty generally reserves taxation to the State of residence of the enterprise unless it carries on business in the other State through a permanent establishment there (article 7.1). Whether your freelance income falls under that article is checked against the treaty’s definitions. For EU citizens, the treaty between Spain and their home country is reviewed in the same way.

Social Security: one country only, set by the rules

Both the EU rules and the EU–UK rules start from the same principle: you are subject to the legislation of a single State. As a general rule, a self-employed person is covered in the State where the activity is carried out. Having clients abroad must be distinguished from carrying out activity abroad; which of the two applies is assessed on the facts.

EU, EEA and Swiss nationals: Regulation (EC) 883/2004

If you work only from Spain, the general rule points to Spanish legislation (article 11.3.a). If you normally carry out self-employed activity in two or more Member States, the legislation of your State of residence applies if you carry out a substantial part of your activity there; otherwise, that of the State where the centre of interest of your activities is located (article 13.2). Self-employed activity in one State combined with employment in another is governed by the employment (article 13.3). Whichever legislation applies treats you as if all your activity and income were in that State (article 13.5).

A substantial part means a quantitatively substantial part, not necessarily the major part. For self-employed activity the indicative criteria are turnover, working time, number of services and income; a share of less than 25%, in an overall assessment, indicates that it is not substantial. The situation projected for the following 12 calendar months is taken into account (Regulation (EC) 987/2009, article 14.8 and 14.10). A person working in two or more States must inform the designated institution of the State of residence, which makes a provisional determination (article 16). The A1 form is the certificate of applicable legislation.

A temporary stay is a different case: a person who normally works as self-employed in one Member State and goes to carry out similar activity in another remains subject to the first State’s legislation if the anticipated duration does not exceed 24 months (Regulation 883/2004, article 12.2). Moving your life to Valencia is not normally a temporary posting.

UK nationals since 2021: the Trade and Cooperation Agreement

The Brexit transition period ended on 31 December 2020 (Withdrawal Agreement, article 126). For situations arising after that date, the Social Security Protocol of the EU–UK Trade and Cooperation Agreement applies. It also starts from a single State (article SSC.10.1) and, as a general rule, a self-employed person is subject to the legislation of the State where the activity is carried out (article SSC.10.3.a).

If you normally work as self-employed in the United Kingdom and in one or more EU States, the legislation of your State of residence applies if you carry out a substantial part of your activity there; otherwise, that of the State where the centre of interest of your activities is located (article SSC.12.2). If you are employed in one State and self-employed in another, the employment decides (article SSC.12.3). The same 25% indicator and 12-month projection apply (Annex SSC-7, article SSCI.13).

Temporary self-employed activity in another State for up to 24 months (article SSC.11.1.b) is a transitional rule that applies only between the UK and the Member States that opted for it under Annex SSC-8. We check Spain’s position before relying on it.

UK nationals already in a cross-border situation at the end of 2020

The Withdrawal Agreement keeps the EU coordination rules (Regulations 883/2004 and 987/2009) for UK nationals who were subject to the legislation of a Member State at the end of the transition period, or who resided in a Member State while subject to UK legislation at that date, among other cases (article 30.1 and article 31.1). They remain covered for as long as they continue, without interruption, in a situation involving both a Member State and the UK (article 30.2). UK nationals who were already residing in Spain under EU law before the end of 2020 and have continued to reside here are also covered, for as long as they keep their right of residence or work under the Agreement (article 30.3 and 30.4). So we check both: your residence status at the end of 2020 and whether your cross-border situation has continued since.

Registering as autónomo: tax and Social Security

Two registrations are involved. The tax registration (census declaration) must be filed before starting the activity (RD 1065/2007, article 9.4). Social Security registration under the self-employed scheme (RETA) applies to people over 18 who carry on an economic or professional activity habitually, personally and directly, on their own account and outside another person’s management and organisation (General Social Security Act, article 305.1). If another country’s legislation applies under the rules above, that is evidenced before registering in RETA, to avoid contributions in two countries.

Our Spanish guide to autónomo registration in Valencia (in Spanish) covers the ordinary domestic case. Where there is a cross-border element, the European or EU–UK analysis comes first.

The residence document is a different matter

For EU and EEA citizens staying more than three months, Royal Decree 240/2007 requires the person to apply in person for entry in the Central Register of Foreign Nationals within three months of arrival; the EU registration certificate is then issued (article 7.5). UK nationals hold a different immigration status. Either way, the residence document is an immigration record: it neither fixes your tax residence nor determines the applicable Social Security legislation. The three must be consistent with each other.

What we review before anything is filed

1. Tax residence: days in Spain, centre of interests, family and, if two countries claim you, the treaty tie-breaker.
2. Actual activity: where you physically work, for whom, and whether you keep work or registration in another country.
3. Social Security: EU rules, EU–UK Protocol or Withdrawal Agreement, and the evidence of applicable legislation.
4. Spanish registrations: tax census and RETA, when they apply.
5. Returns: Spanish returns for the activity and treatment of foreign income and foreign tax.

Sources and review date

Legislation checked on 7 November 2026. We review the version applicable to your period.

• Personal Income Tax Act (Law 35/2006): articles 2, 9 and 12
• Spain–UK tax treaty: articles 4 and 7
• Regulation (EC) 883/2004: articles 11, 12 and 13
• Regulation (EC) 987/2009: articles 14 and 16
• EU–UK Trade and Cooperation Agreement: Social Security Protocol, articles SSC.10 to SSC.12, Annexes SSC-7 and SSC-8
• Withdrawal Agreement: articles 30, 31 and 126
• General Social Security Act (RDLeg 8/2015): article 305
• Royal Decree 1065/2007: article 9, census registration
• Royal Decree 240/2007: article 7