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openaccountants/skills/eu-social-security-coordination.md

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1---
2name: eu-social-security-coordination
3description: >
4 EU social security coordination rules under Regulation (EC) No 883/2004 and Implementing
5 Regulation (EC) No 987/2009. Determines which single EU/EEA/Swiss country's social security
6 legislation applies to a cross-border worker. Use when the user asks about social security
7 for workers active in multiple EU countries, posted workers, A1 certificates, which country
8 to pay social insurance in, multi-state freelancers, or social security coordination between
9 EU member states. Covers posted worker exception, multi-state worker rules, self-employed
10 across borders, simultaneous employment/self-employment, EEA/Switzerland extension, and
11 UK post-Brexit rules under the Trade and Cooperation Agreement.
12version: 1.0
13category: cross-border
14jurisdiction: EU/EEA/CH/UK
15primary_legislation: Regulation (EC) No 883/2004; Regulation (EC) No 987/2009
16---
17 
18# EU Social Security Coordination
19 
20## Skill Metadata
21 
22| Field | Value |
23|-------|-------|
24| Jurisdiction | EU-27, EEA (Iceland, Liechtenstein, Norway), Switzerland, UK (via TCA) |
25| Primary Legislation | Regulation (EC) No 883/2004 on the coordination of social security systems |
26| Implementing Legislation | Regulation (EC) No 987/2009 laying down the procedure for implementing Reg 883/2004 |
27| Key CJEU Rulings | C-743/23 (Sep 2025, "substantial part" calculation); C-694/20 (Dec 2022); C-610/18 (2020, AFMB) |
28| Scope | Determination of applicable social security legislation for persons active in multiple member states |
29| Contributor | OpenAccountants |
30| Validation Date | May 2026 |
31| Skill Version | 1.0 |
32 
33---
34 
35## Section 1 — Core principle: you pay social security in ONE country only
36 
37**Article 11(1) of Regulation 883/2004:**
38 
39> "Persons to whom this Regulation applies shall be subject to the legislation of a single Member State only."
40 
41This is the foundational rule. A person working across EU/EEA borders pays social security contributions in exactly one country. They cannot be required to pay in two countries simultaneously. The entire purpose of Regulation 883/2004 is to determine which single country's legislation applies.
42 
43### What "social security" covers under the Regulation
44 
45The Regulation coordinates ALL branches of social security (Article 3):
46 
47| Branch | Examples |
48|--------|----------|
49| Sickness benefits | Health insurance, sick pay |
50| Maternity and equivalent paternity benefits | Parental leave payments |
51| Invalidity benefits | Disability payments |
52| Old-age benefits | State pension |
53| Survivors' benefits | Widow/widower pension |
54| Benefits in respect of accidents at work and occupational diseases | Work injury insurance |
55| Death grants | Funeral payments |
56| Unemployment benefits | Jobseeker's allowance |
57| Pre-retirement benefits | Early retirement schemes |
58| Family benefits | Child benefit |
59 
60It does NOT cover social assistance, supplementary pension schemes governed by contract, or special non-contributory cash benefits (which are listed in Annex X and non-exportable).
61 
62### Four principles of coordination
63 
641. **Single applicable legislation** — you pay in one country only
652. **Equal treatment** — same rights and obligations as nationals of the country where you're covered
663. **Aggregation** — periods of insurance in other countries count toward benefit entitlements
674. **Exportability** — cash benefits can generally be paid regardless of which country you live in
68 
69---
70 
71## Section 2 — Determination rules: lex loci laboris
72 
73**General rule (Article 11(3)(a)):** The legislation of the member state where the person is **employed or self-employed** applies. This is the "lex loci laboris" (law of the place of work) principle.
74 
75| Situation | Applicable Legislation | Article |
76|-----------|----------------------|---------|
77| Employed in one member state | State where employed | Art 11(3)(a) |
78| Self-employed in one member state | State where self-employed | Art 11(3)(a) |
79| Civil servant | State of the employing administration | Art 11(3)(b) |
80| Receiving unemployment benefits | State providing the benefit | Art 11(3)(c) |
81| Called up for military/civil service | State requiring the service | Art 11(3)(d) |
82| No activity (economically inactive) | State of residence | Art 11(3)(e) |
83 
84**The general rule is simple: you work in country X, you pay social security in country X.** Complications arise only when a person works in multiple countries, is posted abroad, or combines employment and self-employment across borders.
85 
86### What "employed" means
87 
88The Regulation uses the definition of the member state whose legislation is being determined. A person is considered employed or self-employed based on the national law of the relevant member state. There is no EU-wide definition of employment vs self-employment for SS purposes.
89 
90---
91 
92## Section 3 — Posted worker exception (A1 certificate)
93 
94**Article 12 of Regulation 883/2004:**
95 
96An employer may send (post) a worker to another member state while keeping that worker subject to the home country's social security legislation, provided:
97 
98| Condition | Requirement |
99|-----------|-------------|
100| Duration | Maximum 24 months (anticipated duration at outset) |
101| Replacement prohibition | The posted worker must not be sent to replace another posted worker whose posting period expired |
102| Prior insurance | The worker must have been subject to the legislation of the sending state immediately before the posting began |
103| Direct relationship | The worker must remain under the authority of the sending employer during the posting |
104| Employer's substantial activity | The employer must normally carry out substantial activities in the sending state (not merely internal management) |
105 
106### Key limitations
107 
108- The 24-month limit is strict. If the posting is expected to exceed 24 months from the outset, Article 12 does NOT apply.
109- If circumstances change and the posting extends beyond 24 months, an Article 16 agreement (exceptional agreement between competent institutions) can be requested.
110- The worker must have been insured in the sending state BEFORE the posting. You cannot hire someone specifically to post them on day one (though a minimum prior period is not specified in the Regulation, national authorities typically require at least 1 month).
111- The employer must have genuine, substantial business activity in the sending state. A letterbox company with no real activity cannot post workers.
112 
113### A1 certificate for posted workers
114 
115The A1 certificate (Portable Document A1) is the proof that a posted worker remains subject to the sending state's legislation. It is issued by the sending state's competent institution.
116 
117**Until an A1 certificate is obtained, the host country can demand contributions.** The A1 certificate is binding on the host country's institutions and courts (CJEU: A-Rosa Flussschiff, C-620/15) — the host country cannot refuse to accept a valid A1 unless it has been withdrawn or invalidated through the official dispute procedure.
118 
119---
120 
121## Section 4 — Multi-state workers (Article 13)
122 
123A person who **normally** pursues activity in two or more member states simultaneously follows different determination rules.
124 
125### Employed persons in two or more states (Article 13(1))
126 
127| Test | Result |
128|------|--------|
129| Pursues **substantial part** (≥ 25%) of activity in residence state | Residence state's legislation applies |
130| Does NOT pursue substantial part in residence state, employed by ONE employer | Employer's registered office state applies |
131| Does NOT pursue substantial part in residence state, employed by TWO+ employers in same state | That state's legislation applies |
132| Does NOT pursue substantial part in residence state, employed by TWO+ employers in different states (one of which is residence) | Employer state (other than residence) applies |
133| Does NOT pursue substantial part in residence state, employed by TWO+ employers all in states other than residence | Residence state's legislation applies |
134 
135### The 25% substantial activity test
136 
137**Article 14(8) of Implementing Regulation 987/2009:**
138 
139"Substantial part" means a quantitatively substantial part of all activities — measured by:
140 
1411. **Working time** (hours/days worked in the state as a share of total working time), AND/OR
1422. **Remuneration** (pay attributable to work in the state as a share of total pay)
143 
144**The 25% threshold:** If LESS than 25% of either working time or remuneration is in the residence state, a substantial part is NOT being pursued there.
145 
146**CJEU ruling C-743/23 (September 2025):** Confirmed that:
147- The 25% threshold is assessed based on the **projected situation over the next 12 months** from the start of multi-state activity
148- Only working time and remuneration are relevant criteria — nature of work, location of clients, or other factors are irrelevant
149- The assessment includes work in third countries (non-EU) in the denominator when calculating the percentage
150 
151### Determination procedure (Article 16 of Reg 987/2009)
152 
1531. The worker (or employer) notifies the competent institution of the residence state
1542. The residence state provisionally determines applicable legislation
1553. The residence state informs all other states' institutions within 2 months
1564. If no objection within 2 months → determination becomes definitive
1575. If objection → dialogue between institutions; if no agreement within 6 months → refer to Administrative Commission
158 
159**During the provisional period, the worker is subject to the provisionally determined legislation.** This avoids gaps in coverage.
160 
161---
162 
163## Section 5 — Self-employed across borders (Article 13(2))
164 
165| Test | Result |
166|------|--------|
167| Pursues substantial part (≥ 25%) of self-employed activity in residence state | Residence state's legislation applies |
168| Does NOT pursue substantial part in residence state | State where the **centre of interest** of activities is situated |
169 
170### Centre of interest determination
171 
172For self-employed persons not meeting the 25% threshold in their residence state, the "centre of interest" is determined by considering:
173 
174- Where the fixed and permanent premises for the activity are located
175- The habitual nature or duration of activities pursued
176- The number of services rendered
177- The intention of the person as revealed by all circumstances
178 
179**Practical example:** A freelance consultant resident in Belgium who works 60% of the time at clients in the Netherlands and 40% in Belgium → 40% ≥ 25% in residence state → Belgium's legislation applies.
180 
181**Practical example:** A freelance developer resident in Portugal who works 90% for clients accessed remotely from Portugal but the registered business is in Estonia → work is performed in Portugal (≥ 25%) → Portugal's legislation applies.
182 
183---
184 
185## Section 6 — Simultaneous employment and self-employment (Article 13(3))
186 
187**Rule:** A person who normally pursues employment in one state AND self-employment in another state is subject to the legislation of the state where the **employed activity** is pursued.
188 
189| Combination | Applicable Legislation |
190|-------------|----------------------|
191| Employed in state A + self-employed in state B | State A (employment state) |
192| Employed in states A and B + self-employed in state C | Determined per Article 13(1) rules for multi-state employees |
193 
194**Key consequence:** A person employed in Germany who also freelances for clients in France pays ALL social security (including on the freelance income) in Germany. France cannot claim contributions on the self-employed activity.
195 
196**Exception:** If the person pursues employed activity in two or more states AND self-employment in one or more states, the multi-state employee rules of Article 13(1) determine the applicable legislation first, and then that legislation covers ALL activities.
197 
198---
199 
200## Section 7 — A1 certificate: what it is, how to get it, who issues it
201 
202### What the A1 certificate is
203 
204The Portable Document A1 (PD A1) is an official certificate confirming which member state's social security legislation applies to a person. It is proof that the holder does not need to pay contributions in any other member state.
205 
206### When you need an A1 certificate
207 
208| Situation | A1 needed? |
209|-----------|-----------|
210| Posted to another member state for up to 24 months | YES — mandatory before posting begins |
211| Normally working in two or more member states | YES — to confirm which legislation applies |
212| Self-employed temporarily performing activity in another state | YES — mandatory |
213| Business trip (< 2 days, no work performed) | NO — but advisable for evidence |
214| Attending a conference or training | Generally NO — but complex if any "work" is performed |
215 
216### How to obtain an A1 certificate
217 
2181. **Application:** Submit to the competent institution of the state whose legislation you claim applies
2192. **Information required:** Identity details, employer details, nature of activity, countries of activity, anticipated duration, percentage of activity per country
2203. **Processing time:** Varies by country (1–8 weeks typically)
2214. **Validity:** Covers the period specified; for multi-state workers, typically issued for up to 24 months and renewable
2225. **Retroactive issue:** Can be issued retrospectively (but some countries resist this; apply BEFORE activity begins)
223 
224### Issuing authority by country
225 
226| Country | Competent Institution for A1 |
227|---------|------------------------------|
228| Germany | GKV-Spitzenverband (DVKA) / competent Krankenkasse |
229| France | URSSAF / CPAM (depends on scheme) |
230| Netherlands | SVB (Sociale Verzekeringsbank) |
231| Belgium | RSZ/ONSS (employed) / RSVZ/INASTI (self-employed) |
232| Italy | INPS (Istituto Nazionale della Previdenza Sociale) |
233| Spain | TGSS (Tesorería General de la Seguridad Social) |
234| Portugal | ISS (Instituto da Segurança Social) |
235| Austria | ÖGK (Österreichische Gesundheitskasse) |
236| Ireland | Dept of Social Protection, Scope Section |
237| Poland | ZUS (Zakład Ubezpieczeń Społecznych) |
238| Sweden | Försäkringskassan |
239| Denmark | Udbetaling Danmark |
240| Malta | Department of Social Security |
241| Greece | EFKA (e-EFKA electronic system) |
242| Finland | ETK (Finnish Centre for Pensions) |
243 
244### Consequences of not having an A1
245 
246- Host country may demand contributions (and the worker/employer cannot refuse)
247- If contributions are paid in the wrong country, refund procedures apply but take 12–24 months
248- Penalties possible in some countries for working without a valid A1 (especially France: fines for employer)
249- The worker remains covered by the correct legislation regardless of whether the A1 exists — the certificate is declaratory, not constitutive
250 
251---
252 
253## Section 8 — EEA/Switzerland extension
254 
255Regulation 883/2004 applies to:
256 
257| Territory | Basis |
258|-----------|-------|
259| EU-27 member states | Directly applicable EU regulation |
260| Iceland, Liechtenstein, Norway | EEA Agreement (Decision of the EEA Joint Committee No 76/2011) |
261| Switzerland | EU-Switzerland Agreement on the Free Movement of Persons (in force 1 June 2002) |
262 
263The rules apply identically. A person working in Germany and Switzerland follows the same Article 13 determination as a person working in Germany and France.
264 
265**Limitation:** The coordination only works within the EU/EEA/CH block. A person working in Germany and the United States is NOT covered by Regulation 883/2004 for the US portion — a bilateral totalization agreement between Germany and the US (if one exists) governs that relationship.
266 
267---
268 
269## Section 9 — UK post-Brexit (Trade and Cooperation Agreement)
270 
271### Legal basis
272 
273The EU-UK Trade and Cooperation Agreement (TCA), signed 30 December 2020, contains a **Protocol on Social Security Coordination** that provides continued coordination for persons moving between the EU and the UK after 1 January 2021.
274 
275### Who is covered
276 
277| Persons | Coverage |
278|---------|----------|
279| Persons covered by the Withdrawal Agreement | Continue under the WA (more comprehensive rights) |
280| Persons NOT covered by the WA who move between EU and UK after 1 Jan 2021 | Covered by TCA Protocol |
281| Third-country nationals moving between EU and UK | Generally NOT covered by TCA Protocol (unlike Reg 883/2004 which covers all nationalities) |
282 
283### Key TCA rules (similar to but narrower than Reg 883/2004)
284 
285| Rule | TCA Provision |
286|------|--------------|
287| Single applicable legislation | Article SSC.10 — same principle as Art 11 of 883/2004 |
288| Lex loci laboris | Article SSC.10(3) — same general rule |
289| Posted workers | Article SSC.11 — maximum 24 months (same as Art 12) |
290| Multi-state workers | Article SSC.12 — similar to Art 13 (25% test applies) |
291| A1-equivalent certificate | PDA1 certificate issued under TCA provisions |
292 
293### Key differences from Reg 883/2004
294 
295| Difference | Impact |
296|-----------|--------|
297| No aggregation for unemployment in some cases | UK workers moving to EU may not aggregate UK periods for unemployment benefit |
298| Healthcare limited | No EHIC for new cases; S1 for pensioners continues |
299| Family benefits limited | No export of family benefits in all cases |
300| Nationality restriction | TCA covers EU and UK nationals (not all nationalities like 883/2004) |
301| No planned revision process | Unlike 883/2004 which has an ongoing revision proposal |
302 
303### Practical guidance for UK-EU cross-border workers
304 
305- A UK national posted from the UK to France: TCA Art SSC.11 applies → A1-equivalent from HMRC → continue UK NIC for up to 24 months
306- A UK company hiring a remote worker in Spain: Worker is subject to Spanish SS → employer registers with Spanish TGSS
307- A freelancer resident in UK working 50% UK / 50% Germany: TCA Art SSC.12 → substantial part in UK (50% ≥ 25%) → UK NIC applies to all activity
308 
309---
310 
311## Section 10 — Common scenarios with worked examples
312 
313### Scenario A — Remote worker for foreign employer
314 
315**Facts:** Maria lives in Portugal. She is employed full-time by a German company (GmbH). She works 100% remotely from her home in Lisbon. She never travels to Germany.
316 
317**Analysis:**
318- Maria pursues activity in ONE state only (Portugal — where work is physically performed)
319- Article 11(3)(a) applies: legislation of the state where employed = Portugal
320- Maria is subject to Portuguese social security
321- German employer must register as employer with Portuguese ISS and pay Portuguese contributions
322 
323**Result:** Portugal. The German employer registers with ISS, pays employer/employee contributions per Portuguese rates.
324 
325### Scenario B — Posted worker
326 
327**Facts:** Johann works for a Munich-based engineering firm. He is sent to oversee a construction project in Austria for 18 months. He will return to Munich afterwards.
328 
329**Analysis:**
330- Article 12 posting rules apply
331- Duration: 18 months < 24 months maximum ✓
332- Johann was previously insured in Germany ✓
333- Employer has substantial activity in Germany ✓
334- Not replacing another posted worker ✓
335 
336**Result:** Germany continues to apply. Employer obtains A1 from GKV-Spitzenverband (DVKA). Johann does NOT pay Austrian social security.
337 
338### Scenario C — Multi-country freelancer
339 
340**Facts:** Sophie is a freelance UX designer resident in Belgium. She works 30% of her time for clients in Belgium, 40% in the Netherlands, and 30% in France.
341 
342**Analysis:**
343- Article 13(2) for self-employed in multiple states
344- Does Sophie pursue a substantial part in her residence state (Belgium)? 30% ≥ 25% → YES
345- Belgium's legislation applies to ALL of Sophie's self-employed activity
346 
347**Result:** Belgium. Sophie pays Belgian self-employed social security (RSVZ/INASTI) on her entire worldwide self-employed income. No contributions owed in NL or FR.
348 
349### Scenario D — Employee plus freelancer in different countries
350 
351**Facts:** Marco is employed in Italy (full-time software engineer at an Italian company). He also freelances as a consultant for German clients, performing this work from his home in Italy.
352 
353**Analysis:**
354- Article 13(3): employed + self-employed in different states
355- Employed activity in Italy → Italy's legislation applies to ALL activity
356- BUT: the freelance work is ALSO performed in Italy (from home) → this is actually a single-state case
357- Italy's legislation applies regardless
358 
359**Result:** Italy. INPS contributions on both employed and self-employed income. No German obligation.
360 
361### Scenario E — UK employee working partly in EU post-Brexit
362 
363**Facts:** James is a UK resident employed by a UK company. He works 3 days/week from London (60%) and 2 days/week from the company's Paris office (40%).
364 
365**Analysis:**
366- TCA Protocol Art SSC.12 (multi-state worker)
367- James is resident in UK. Does he pursue ≥ 25% in UK? 60% ≥ 25% → YES
368- UK legislation applies to all activity
369 
370**Result:** UK. James pays UK NIC on all earnings. French contributions not owed. Employer obtains PDA1 from HMRC confirming UK coverage.
371 
372---
373 
374## PROHIBITIONS
375 
3761. **NEVER** tell a user they must pay social security in two EU/EEA countries simultaneously. The fundamental principle is single applicable legislation.
3772. **NEVER** assume that the country where a person is resident is automatically the competent SS state. Lex loci laboris means the country of WORK generally applies.
3783. **NEVER** advise that an A1 certificate is "optional" or "nice to have." For posted workers and multi-state workers, it is the essential proof document.
3794. **NEVER** assume Regulation 883/2004 applies to non-EU/EEA/CH countries. For US, Canada, Australia, etc., bilateral totalization agreements (if they exist) govern.
3805. **NEVER** compute contribution amounts. This skill determines WHICH country — the country skill provides the rates and computation.
3816. **NEVER** advise creating artificial posting arrangements to avoid higher contributions in the host state. This is a known abuse pattern and authorities actively investigate it.
382 
383---
384 
385## Disclaimer
386 
387This skill and its outputs are provided for informational and computational purposes only and do not constitute tax, legal, or financial advice. Open Accountants and its contributors accept no liability for any errors, omissions, or outcomes arising from the use of this skill. Social security coordination determinations are fact-specific and have significant financial consequences. All outputs must be reviewed and signed off by a qualified social security coordination specialist before acting upon.
388 
389The most up-to-date, verified version of this skill is maintained at [openaccountants.com](https://openaccountants.com). Log in to access the latest version, request a professional review from a licensed accountant, and track updates as tax law changes.
390 

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EU social security coordination rules under Regulation (EC) No 883/2004 and Implementing Regulation (EC) No 987/2009. Determines which single EU/EEA/Swiss country's social security legislation applies to a cross-border worker. Use when the user asks about social security for workers active in multiple EU countries, posted workers, A1 certificates, which country to pay social insurance in, multi-state freelancers, or social security coordination between EU member states. Covers posted worker exception, multi-state worker rules, self-employed across borders, simultaneous employment/self-employment, EEA/Switzerland extension, and UK post-Brexit rules under the Trade and Cooperation Agreement.

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