In 2024, Member States and EFTA countries issued 5.6 million Portable Document A1s, according to the European Commission's Annual Report on Intra-EU Labour Mobility 2025 Edition, a 0.8 percent increase on the 5.5 million issued in 2023.
Of those certificates, 3.61 million were issued under the posting rule in Article 12 of Regulation (EC) No 883/2004, covering about 2.23 million people.
Most of the postings were short: 64 percent lasted around one month.
That volume is why A1 is a standing social-security control, not a form reserved for long assignments.
Rise is a global payroll and Employer of Record platform for companies that hire and pay people across borders without standing up a local entity in every market.
An A1 is the social-security certificate for a genuine posting inside the EU, the EEA, and Switzerland.
This article explains what the document is, the legal rule behind it, when posted workers need one, how to apply and how long coverage lasts, what host authorities can do if it is missing, and how finance and HR should run the process before work starts.
Key Takeaways
An A1, or Portable Document A1, is the official statement of which country's social-security legislation applies to a worker who is posted, or who works in two or more countries, inside the EU, the EEA, or Switzerland.
Regulation (EC) No 883/2004 puts a person under one country's legislation only. Article 12 lets a genuine posting remain on home-country social security if the anticipated duration does not exceed 24 months and the worker is not sent to replace another person.
The employer should apply to the home-country institution before the posting starts. Your Europe states that posted workers must, as a general rule, have been registered in the home social insurance system for at least one month before being posted.
Without a valid A1, the host can assess local social contributions on top of home contributions. The certificate is the proof that contributions stay in one system.
A1 is not shadow payroll and not permanent establishment. Use an Employer of Record when the person should be employed locally rather than posted.
What an A1 Certificate Is
A Portable Document A1 is the official statement of applicable social-security legislation.
It replaced the older E 101 certificate.
The home-country social-security institution issues it.
If the person is posted, that institution is in the sending country.
The document confirms that the holder is subject to one country's legislation and that contributions for the covered period are not due in the host country of work.
It is issued for named start and end dates, not as an open-ended affiliation.
It covers the statutory branches coordinated by the Regulation, including sickness, old-age, unemployment, and accidents at work.
It does not decide income-tax residence, immigration status, or whether the employer has a corporate taxable presence.
The worker or employer should be able to present it during a labour-inspectorate or social-security check.
As long as the A1 is valid, host authorities must recognise it.
Outside the EU, the EEA, and Switzerland, the analogue is a totalization agreement and a certificate of coverage.
The US Social Security Administration, for example, issues a certificate of coverage so that a detached worker is not taxed for social security in two countries on the same earnings.
That is a different legal instrument.
The Legal Rule in Regulation (EC) No 883/2004
The default rule is the place of work.
Article 11(1) of Regulation (EC) No 883/2004 is explicit: persons to whom the Regulation applies shall be subject to the legislation of a single Member State only.
Article 11(3)(a) then says that a person pursuing an activity as an employed or self-employed person in a Member State shall be subject to the legislation of that Member State.
A posting is the main exception.
Article 12(1) provides that a person who pursues an activity as an employed person in a Member State on behalf of an employer which normally carries out its activities there, and who is posted by that employer to another Member State to perform work on that employer's behalf, shall continue to be subject to the legislation of the first Member State, provided that the anticipated duration of such work does not exceed twenty-four months and that he is not sent to replace another person.
Article 12(2) applies the same 24-month limit to a self-employed person who goes to pursue a similar activity in another Member State.
Two conditions in that text get missed on mobility checklists.
First, the anticipated duration must not exceed 24 months.
If the assignment is known from the outset to last longer, Article 12 is the wrong route.
Second, the worker must not be sent to replace another posted person.
Rotating staff through the same host role to keep home-country affiliation is not a posting under Article 12.
The employer must also normally carry out activities in the sending state, and the work abroad must be performed on that employer's behalf.
An A1 certifies those facts; it does not create them.
Article 13 covers a different pattern: a person who normally pursues an activity in two or more Member States.
Your Europe treats a "substantial part" of activity as at least 25 percent of working time and/or income in the country of residence.
If that test is met, residence-country legislation generally applies.
The A1 is still required.
It is the proof of which legislation was determined.
Article 16 lets two or more Member States agree, in the interest of the person, on an exception to Articles 11 to 15.
That is the legal basis for many extensions beyond 24 months.
When Posted Workers Need One
Posted workers need an A1 when they are sent by an employer in one EU, EEA, or Swiss country to work temporarily in another, and the company intends to keep them on home-country social security.
Your Europe treats posting as sending a staff member to another EU country for a specific period to provide services to a business partner, or to work in a business the employer owns there.
An employment relationship with the posting employer must exist.
EU posting rules also apply to third-country nationals who are legally residing in a Member State and are then posted.
As a general rule, posted workers must have been registered in the home country's social insurance system for at least one month before being posted.
The A1 is required even when the posting is short.
The Commission's 2024 figures show that most postings last around one month.
Business trips are not postings under employment law when the worker is only attending conferences, meetings, fairs, or training.
Your Europe still requires the employer, for social security, to inform the host administration whenever possible in advance and request a Portable Document A1.
Self-employed professionals who go to pursue a similar activity in another Member State need an A1 under Article 12(2).
Employees who regularly work in two or more countries need an A1 under Article 13.
If the person is moving permanently, or if the host country is becoming the place of work rather than a temporary posting, Article 12 does not apply.
That is a local employment or Employer of Record decision, not an A1 decision.
How to Apply, How Long It Lasts, and How to Extend
The employer applies to the competent social-security institution in the country where the employee is insured.
The Commission is explicit that the employer should apply for the A1 before the period of posting starts.
Your Europe requires the employer to specify the start and end date of the posting.
The maximum period that can be indicated on the form is 24 months.
Processing can take several weeks, and HMRC notes that a delay of several months is not uncommon.
The posting declaration to the host labour authorities is a separate filing.
Your Europe requires the employer to notify the host before, or at the latest when, the posting begins.
The A1 does not replace that notification.
The notification does not replace the A1.
If the posting lasts longer than 24 months, or needs to be prolonged, Your Europe gives two options.
The employer can request the issuer of the PD A1 to grant an extension, which is not granted automatically and is subject to a mutual agreement between the home and host countries.
Or the employee can subscribe to the social-security system of the host country.
Contact the issuing institution before the current A1 expires.
Your Europe notes that a further posting usually waits until a period has elapsed since return, and that two months is considered sufficient by many EU countries.
The A1 is not a substitute for host-country employment conditions.
Posted workers must still receive the host's core employment terms where those terms are more favourable, and the 12-month long-term posting rule is a different clock from the 24-month social-security limit.
What Happens Without an A1
Without a valid A1, the host country can treat the worker as subject to its own social-security legislation from the first day of work.
The Finnish Centre for Pensions states the consequence in operational terms: a foreign authority has the right to demand that statutory social insurance contributions for the work are paid in the country where the work is done.
HMRC's instruction for inbound workers claiming exemption under Article 12 is to charge primary and secondary National Insurance until they produce the Portable Document A1.
Until the certificate is produced, the host assessment stands.
Home contributions often continue because the home payroll has not been told to stop.
Host contributions are assessed because there is no certificate telling the host to stand down.
Untangling the overlap after the fact is slow, and refunds depend on the two institutions agreeing which legislation actually applied.
If home affiliation is not certified, home sickness cover, pension accrual, and the European Health Insurance Card can also fail for the period of work abroad.
The A1 is binding on host institutions while it is valid.
A host that doubts the facts must use the official dialogue procedure between institutions rather than ignore the certificate.
Until the issuing institution withdraws it, the host must recognise it.
Applying late is not a strategy, because uncovered days remain exposed.
A1 Is Not Shadow Payroll, and It Is Not Permanent Establishment
Three files get mixed together on the same assignment.
Keep them separate.
An A1 answers which country's social-security legislation applies to the worker.
Shadow payroll is the host reporting rail for income tax, and sometimes for social contributions, when the employee stays on home payroll.
Permanent establishment is whether the company itself has a taxable presence in the host country.
An A1 does not file host income tax.
A shadow-payroll run does not certify applicable social-security legislation under Regulation 883/2004.
Neither document answers the OECD Article 5 question about the enterprise.
Once that distinction is drawn, the operating question is A1.
If the facts are a genuine, time-limited posting from an employer that normally carries out activities at home, apply for the A1 before work starts and keep home social contributions running.
If the facts are a lasting host-country job, do not stretch Article 12.
Move the person onto a local contract through a host entity or an Employer of Record, and register for host social security.
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An Agent of Record is only for a genuine contractor.
How to Operationalize A1s Before Work Starts
Treat A1 as a pre-travel control, the same way legal and compliance teams already treat work authorisation and host notifications.
1. Decide whether the facts are a posting.
Article 12 requires a home employer that normally carries out activities there, work performed on that employer's behalf, an anticipated duration of no more than 24 months, and no replacement of another posted person.
If the person already lives and works in the host country, or if the role is open-ended, it is not a posting.
2. Confirm prior home-country affiliation.
Your Europe's one-month registration rule is the baseline.
A new hire flown out in week one will often fail it.
3. File the A1 before departure, and file the host posting declaration as a separate step.
Put both on the same assignment checklist, with the start and end dates that will appear on the certificate.
4. Calendar the 24-month social-security limit separately from the 12-month employment-conditions limit.
They are different clocks.
An extension under Article 16 needs a mutual agreement, started before the current A1 expires.
5. Keep the issued certificate where operations can produce it.
Site access and payroll audits ask for the same PDF, and date changes must be notified to the issuing institution and the host.
6. Reassess the employment model when the posting stops being temporary.
That is the point at which how you set up global payroll matters more than another portable document.
A local contract through an owned entity or an Employer of Record replaces the posting; it does not sit on top of a lapsed A1.
Conclusion
A1 is the certificate that makes the one-country rule in Regulation 883/2004 visible to a host inspector.
The volume is no longer a construction-sector specialty: 5.6 million documents were issued in 2024, and most postings lasted around one month.
The legal limit for a genuine posting is 24 months, with no replacement of another posted person, and the application belongs with the home institution before work starts.
Without the document, the host can assess social contributions on top of home contributions.
With it, contributions stay in one system for the named period.
Get the A1 right on a true posting, and change the employment model when the posting is no longer true.
Book a demo with the Rise team to map current EU, EEA, and Swiss assignments onto the right social-security and employment path before the next posting window opens.
FAQs
1. What is an A1 certificate?
An A1, or Portable Document A1, is the official statement of which country's social-security legislation applies to a person working across borders in the EU, the EEA, or Switzerland.
It is issued by the institution of the country where the person is insured.
It proves that contributions for the covered period are payable in that country and not in the host country of work.
2. When do posted workers need an A1?
Whenever an employer in one Member State, EEA country, or Switzerland posts an employee to another to work temporarily on that employer's behalf and wants home-country social security to continue.
The same document is needed for many self-employed postings and for people who normally work in two or more countries.
Your Europe also expects an A1 for social-security purposes on business trips that are not postings under employment law.
3. How long does an A1 last?
For a posting under Article 12, the anticipated duration on the form cannot exceed 24 months.
If the posting needs to continue, the employer can request an extension by mutual agreement between the home and host institutions, or move the person onto host-country social security.
Article 13 multi-state certificates are also issued for a defined period and must be renewed when the pattern continues.
4. What happens if you work without an A1?
The host can require local social-security registration and contributions from the first day of work, on top of home contributions that have not been switched off.
HMRC's instruction is to charge National Insurance until the A1 is produced.
Home sickness cover, pension accrual, and the European Health Insurance Card can also fail for the period of work abroad.
5. Is an A1 the same as shadow payroll or permanent establishment?
No.
An A1 decides which social-security legislation applies to the worker.
Shadow payroll is host tax and social reporting for someone who stays on home payroll.
Permanent establishment is whether the company has a taxable presence.
A valid A1 does not remove host wage-tax or PE analysis, and a shadow-payroll file does not replace the A1.