A1 Certificate: What the Portable Document A1 Proves, Who Needs It and How It Works

Employers, payroll teams and institutions also call it the "A1 form" or "form A1"; all three labels name the same document, which replaced the E 101 certificate on 1 May 2010.

The A1 is used in 32 States: the 27 EU Member States, Iceland, Liechtenstein, Norway and Switzerland under Regulation (EC) No 883/2004, and the United Kingdom under the Protocol on Social Security Coordination of the EU-UK Trade and Cooperation Agreement. The A1 matters because the institutions of the host State are bound by it as long as the issuing State has not withdrawn it or declared it invalid, so contributions are paid in one State only. The A1 answers the social security question, and it is one document among the EU rules for posted workers.

This guide explains what the A1 proves and what it leaves out, who needs one under Title II of Regulation (EC) No 883/2004, whether EU law makes it mandatory, which A1 rules have applied since 1 November 2026 and which apply from 2 November 2028, and how many A1s institutions issue each year. Six detailed guides then cover the application, business trips, validity, the issuing institutions, the document itself and the self-employed.

What Is an A1 Certificate?

An A1 certificate is a standard EU document, issued by the social security institution of the State whose legislation applies, that proves which single national social security system covers a person working across borders, so that contributions are paid in one State only. The document answers one question for a defined person and period: which State's social security legislation applies. Posted employees, self-employed persons working temporarily abroad and people who work in two or more States all prove their applicable legislation with it.

The legal basis of the A1 is Article 19(2) of Regulation (EC) No 987/2009, the implementing regulation to Title II of Regulation (EC) No 883/2004. Title II sets the core principle: a person is subject to the legislation of a single Member State only (Article 11(1) of Regulation (EC) No 883/2004), and that State is normally the State where the work is done (Article 11(3)(a)). Articles 12 to 16 of Regulation (EC) No 883/2004 contain the special rules that depart from this place-of-work principle, such as posting, work in two or more States and exception agreements. The A1 is the proof that one of these special rules, or another Title II rule, points to a State other than the place of work.

Article 19(2) of Regulation (EC) No 987/2009 also describes what the A1 states: at the request of the person or the employer, the competent institution of the Member State whose legislation applies certifies that this legislation applies and, where appropriate, until what date and under what conditions. Since 1 November 2026, this attestation is issued in a standardised format under Article 19(2) as amended by Regulation (EU) 2026/2359. Both Regulations have applied since 1 May 2010, the day the A1 came into use. Behind the document, the institutions exchange the underlying data electronically through EESSI (Electronic Exchange of Social Security Information), for which the European Commission lists 32 participating countries as of 5 November 2026.

What the Portable Document A1 Certifies and What It Leaves Out

The A1 certifies one thing: which State's social security legislation applies to the holder for the period shown. This statement draws its value from the single-legislation principle of Article 11(1) of Regulation (EC) No 883/2004: the holder pays contributions under one legislation only, and the institutions of the other States rely on the attestation instead of examining the case afresh.

The A1 binds the institutions of other States until the issuing State withdraws it or declares it invalid (Article 5(1) of Regulation (EC) No 987/2009), as the Court of Justice has held for these certificates since Fitzwilliam (C-202/97, 10 February 2000). A host court may disregard a certificate only for fraud, after the dialogue procedure between the institutions was promptly initiated and the issuing institution failed to review the certificate within a reasonable time (C-359/16 Altun, 6 February 2018; C-370/17 and C-37/18 Vueling, 2 April 2020). Retroactive issue, withdrawal and the dialogue procedure are covered in the validity guide listed below.

The binding effect is limited to social security: in C-17/19 Bouygues travaux publics (14 May 2020), the Court of Justice held that the certificate binds host courts solely in the area of social security. It therefore leaves out host labour law and pay, tax, residence and work permits and medical treatment abroad, each of which follows its own rules.

From the E 101 to the Portable Document A1

The A1 replaced the E 101 certificate on 1 May 2010, when Regulations (EC) No 883/2004 and No 987/2009 replaced Regulations (EEC) No 1408/71 and No 574/72. The E 101 attested the applicable legislation under the old Regulations, and the Your Europe forms page still names it as the predecessor of the portable document A1. Older contracts, rulings and guidance that mention an "E 101" or an "A1/E 101 certificate" refer to the same function under the earlier rules; the current document is the A1, never an E 101.

The leading judgments on binding effect, from Fitzwilliam in 2000 to Altun in 2018 and Vueling in 2020, concerned E 101 certificates, and they still guide how the A1 is treated: the 2020 Bouygues judgment covers both the E 101 and the A1. The old rules did not end everywhere on the same day. Regulation (EEC) No 1408/71 continued to apply with Switzerland until 31 March 2012, and between Switzerland and the other EFTA States until 31 December 2015.

Six A1 Topics in Detail: From Application to Issuing Institution

Six guides take the A1 further: how to apply, when a business trip needs one, how long it is valid and when it binds, who issues it, what the document looks like and how the self-employed obtain one. Each guide answers one question with its legal basis in Regulation (EC) No 987/2009 or Regulation (EC) No 883/2004 and marks the rules that change on 2 November 2028. The table lists the six guides in the order a posting usually raises the questions. The A1 is only one step of a posting: the host State's labour-law notification, host pay and the documents kept at the workplace follow separate rules.

Every obligation before, during and after a posting is listed in the posting compliance checklist.

Who Needs an A1 Certificate?

A worker or self-employed person needs an A1 whenever work takes them from one of the 31 EU, EEA and Swiss States into another while the legislation of a State other than the place of work continues to apply under Title II of Regulation (EC) No 883/2004, and the same holds between the UK and the EU under the TCA Protocol. The four groups that fall under this rule are listed below, each with its own article, period and applicant.

• Posted employees, sent by their employer to work in another State
• Self-employed persons who work temporarily in another State
• People who normally work in two or more States
• Three special groups: civil servants, seafarers, and flight and cabin crew

An employee keeps the sending State's legislation if the anticipated duration of the work does not exceed 24 months and the employee is not sent to replace another person (Article 12(1) of Regulation (EC) No 883/2004). Administrative Commission Decision No A2 of 12 June 2009 sets the indicators the issuing institution checks, such as at least one month's prior affiliation to the sending State's scheme for a person recruited to be posted, the indication that applies until 1 November 2028. Beyond 24 months, the sending State's legislation can continue only under an exception agreement between the States concerned under Article 16(1) of Regulation (EC) No 883/2004. This 24-month period is the social security clock; the 12-month and 18-month thresholds of long-term posting under Directive 96/71/EC are a labour-law clock and run separately.

A self-employed person who normally works in one State and goes to another to pursue a similar activity keeps the home State's legislation for an anticipated duration of up to 24 months (Article 12(2) of Regulation (EC) No 883/2004). The self-employed person requests this A1 personally, from the institution of the home State.

A person who normally works in two or more Member States is subject to one legislation only, determined under Article 13 of Regulation (EC) No 883/2004, and the A1 comes from the designated institution of the State of residence (Article 16 of Regulation (EC) No 987/2009). Under Article 14(8) of Regulation (EC) No 987/2009, a share of less than 25 % of working time and/or remuneration in the State of residence is an indicator that a substantial part of the activity is not pursued there. Habitual cross-border telework of at least 25 % and less than 50 % of working time in the State of residence can stay under the legislation of the employer's State through the Framework Agreement concluded under Article 16(1) of Regulation (EC) No 883/2004, in the States that signed it.

Three special groups follow Article 11 rules rather than a posting: civil servants remain under the legislation of the State of the employing administration (Article 11(3)(b)), seafarers come under the flag State (Article 11(4)), and flight and cabin crew are linked to the State of their home base (Article 11(5) of Regulation (EC) No 883/2004). The rules for each group are set out under social security for posted workers.

Between the United Kingdom and the EU, a detached worker keeps the sending State's legislation for up to 24 months under Article SSC.11 of the Protocol on Social Security Coordination of the Trade and Cooperation Agreement, for employed and self-employed persons alike, and all Member States have opted in to this rule. The table below sets out the seven situations, the article each rests on, its maximum period and who requests the A1.

Is an A1 Certificate Mandatory?

EU law today does not make the A1 a precondition for working abroad: Article 15(1) of Regulation (EC) No 987/2009 asks the employer to inform the competent institution whenever possible in advance, and the A1 is the evidence the host State's institutions accept. The A1 shows which legislation applies; the applicable legislation itself follows from Title II of Regulation (EC) No 883/2004. Whether a host State asks to see the A1 during a posting depends on that State's own posting law.

The A1 is also not the labour-law notice. Posting a worker to provide a service triggers a second, separate duty under labour law: the notification of posted workers that host States require through posting declarations.

The two duties differ in timing. The declaration falls due at the latest at the commencement of the service provision under Article 9(1)(a) of Directive 2014/67/EU, as transposed into each host State's law, while EU law today sets no deadline for the A1 request beyond "whenever possible in advance". A missing declaration and a missing A1 therefore fall under different rules.

National posting laws can add a duty to keep the A1 at the workplace. Austria is one example, as of 5 November 2026: § 21(1) of the Austrian Wage and Social Dumping Act (LSD-BG) requires the A1 to be kept at the workplace or made electronically accessible or, where it could not be obtained before the posting, the A1 application together with proof of foreign social security cover. § 26(1) Z 3 LSD-BG fines a missing A1 up to EUR 20,000 per offence, regardless of the number of workers.

From 2 November 2028, the request becomes a prior notification under Article 15(1) of Regulation (EC) No 987/2009 as replaced, set out in the next section, and a missing notification does not by itself change the applicable legislation. National fines for missing documents are compared under posting penalties.

What Changes for the A1 in 2026 and 2028

Regulation (EU) 2026/2359 of 7 October 2026 has been in force since 1 November 2026: a first set of A1 rules applies already, and the new posting rules apply from 2 November 2028. Regulation (EU) 2026/2359 was published in the Official Journal on 27 October 2026 and amends both Regulation (EC) No 883/2004 and Regulation (EC) No 987/2009. Its two dates divide every A1 question into what applies today and what applies from 2 November 2028.

Since 1 November 2026, the A1 is issued in a standardised format (Article 19(2) of Regulation (EC) No 987/2009 as amended), and the issuing institution issues it only after a proper assessment of the facts and confirmation that the information is correct (new Article 19(3)). Two definitions apply from the same date: fraud (Article 1(2)(ea)) and business trip (Article 1(2)(eb) of Regulation (EC) No 987/2009). The business-trip definition does not exempt any trip today: it prepares an exemption from prior notification that applies only from 2 November 2028, and until then no EU rule exempts a business trip.

From 2 November 2028, under Regulation (EC) No 987/2009 as amended, the employer notifies the competent institution before the activity starts, with an A1 request, and receives an automatic acknowledgement where the A1 is not issued at once (Article 15(1) and (1a)). Business trips, and activities of no more than three consecutive days of work within 30 consecutive days except the construction work listed in Annex 6, are exempt from this prior notification (Article 15(1b)). A person recruited to be posted needs at least three months' prior affiliation instead of one month (Article 14(1)). After 24 months of posting in total, Article 12 of Regulation (EC) No 883/2004 does not apply again for the same State until two months have passed (Article 14(1a)). Where an error is found in an A1, the issuer withdraws or rectifies it within 30 working days (Article 19a(2)).

Persons sent before 2 November 2028 keep the old Article 12 of Regulation (EC) No 883/2004 for that posting (Article 87b(4)), so existing A1s do not lapse on that date. The take-over of Regulation (EU) 2026/2359 by Norway, Iceland, Liechtenstein and Switzerland is pending as of 5 November 2026. Every amended article is listed under what the revision changes.

The table compares seven A1 topics today and from 2 November 2028, as of 5 November 2026.

The Digital A1: A Pending Proposal

A fully digital A1 is only proposed: the Commission tabled COM(2026) 980 on 15 September 2026 (procedure 2026/0271(COD)), and as of 5 November 2026 it awaits a committee decision in the European Parliament's EMPL committee. The referral to the committee was announced on 19 October 2026, and the rapporteur was appointed on 4 November 2026. The proposed regulation on digitalising the coordination of social security systems is known as the European Social Security Pass (ESSPASS).

Under the proposal, the portable document A1 would be issued in digital form one year after the regulation enters into force, and a physical document would remain available on request, carrying a QR code or other electronic features. The Commission estimates that the change would save up to EUR 157 million in A1 fraud over 12 years; this figure is the Commission's own estimate in the proposal. Until the proposal is adopted, the A1 rules described above continue to apply.

How Many A1 Certificates Are Issued?

Institutions issued 5.2 million portable documents A1 in the EU in 2023, according to the Commission staff working document SWD(2026) 982, which estimates 10.8 million for 2040. That projection is an increase of 106 %. The Commission's ESSPASS page gives a different figure, 5.6 million portable documents A1 issued every year, without naming a reference year.

The same staff working document estimates that 0.1 % to 1 % of portable documents are falsified, which corresponds to 3,500 to 35,000 cases a year, and gives a fraud estimate of about EUR 7.5 million a year for the PD A1. Checking one PD A1 takes 5 to 16 minutes today, according to the same document. Each figure below carries its own source, because the two Commission documents give different annual totals.

What an A1 Certificate Does Not Settle

An A1 settles social security only: it does not decide cover outside the 32 States, the labour-law notification, host pay, tax or the right to work. Each of these questions follows its own instrument, and the three answers below name it.

What Replaces the A1 Outside the EU, EEA, Switzerland and the UK?

Outside the 32 States no A1 exists: where a bilateral social security agreement applies, it decides cover, and the sending institution issues a certificate of coverage under it.

A certificate of coverage is not an A1, even where it serves the same purpose for the two States that signed the agreement: it rests on the agreement's own posting article and periods, not on Regulation (EC) No 883/2004. Each agreement is explained under social security agreements.

No A1 is available for a posting to any of the ten countries listed below.

• United States
• India
• Canada
• Turkey
• China
• Japan
• Australia
• Korea
• Brazil
• Serbia

Does an A1 Replace the Labour-Law Notification?

No: the A1 answers the social security question, while the host State's notification of posted workers rests on Article 9(1)(a) of Directive 2014/67/EU and is filed separately. The A1 comes from the competent institution of the State whose legislation applies, the posting declaration goes to the host State, and neither document replaces the other. An employer posting a worker to provide a service in another Member State therefore handles both.

Does an A1 Cover Tax, Labour Law or a Work Permit?

No: an A1 binds only in social security (Bouygues), so host labour law, tax and immigration permits follow their own rules. Tax follows the tax law of the States concerned, and a permit follows the host State's immigration law; neither appears on an A1.

Labour law is the closest neighbour of the A1: posted workers are guaranteed the host State's terms and conditions of employment on the matters listed in Article 3(1) of Directive 96/71/EC, remuneration included, as amended by Directive (EU) 2018/957. Host pay and conditions are set by the Posting of Workers Directive.