A1 Certificate Validity: Duration, Retroactive Issue, Binding Effect and Withdrawal

The A1 is the attestation of Article 19(2) of Regulation (EC) No 987/2009, in which the competent institution certifies that its legislation applies and, where appropriate, until what date and under what conditions. It shows which social security legislation covers the holder in the eyes of other States, which matters for posted workers in the EU.

The page follows the questions in order: the period and its end date, national practice, late issue, the binding effect, withdrawal today, the changes from 2 November 2028 and the steps that keep an A1 valid.

How Long Is an A1 Certificate Valid?

An A1 is valid for the period shown on it: for a posted employee or a self-employed person doing a similar activity, that period is the anticipated duration of the work abroad and may not exceed 24 months (Article 12(1) and (2) of Regulation (EC) No 883/2004). These 24 months belong to the social security clock and are separate from the labour-law clock of Directive 96/71/EC.

Article 19(2) of Regulation (EC) No 987/2009 makes the institution state "until what date and under what conditions" the legislation applies. Since 1 November 2026, Article 19(2) and (3) as amended by Regulation (EU) 2026/2359 require a standardised format and a proper assessment of the facts before the A1 is issued, so the end date on the A1 is the first thing to read in what the A1 certificate proves.

What Happens When the A1 Validity Period Ends

When the end date on the A1 passes, the A1 no longer shows that the sending State's legislation applies, and the general rules of Title II of Regulation (EC) No 883/2004 decide again which State's law covers the work. A posting cannot be stretched past 24 months under Article 12 of that Regulation; only an exception agreement between the States under Article 16(1) keeps the home legislation longer.

Today Decision No A2 of the Administrative Commission asks for two months between postings of the same worker by the same undertakings to the same State.

Validity Periods in National Practice

Issuing institutions describe the period and late requests in their own words, and five of them are shown below with the date each page was checked.

National procedures and processing times stay on the country pages.

Can an A1 Certificate Be Issued Retroactively?

Yes: the Court of Justice held in Banks (C-178/97, 30 March 2000) that an E 101 certificate may have retroactive effect, and in Alpenrind (C-527/16, 6 September 2018) that an A1 may be issued during or after the period concerned and binds retroactively even where the worker was already affiliated in the host State. The A1 is therefore not tied to the day the work starts.

Article 15(1) of Regulation (EC) No 987/2009 asks the employer to inform the competent institution "whenever possible in advance", so a later issue is possible under EU law but not the planned route. From 2 November 2028, Article 20(4) of that Regulation as amended says an attestation issued subsequently shall, where appropriate, have retroactive effect, and Article 15(1) as amended moves the information to "before the start of the activity".

Practice on late requests for short trips differs between States, as the German row above shows, and the page on A1 certificate for business trips explains when a short trip needs an A1 at all.

What Binding Effect Does a Valid A1 Have in the Host State?

A valid A1 binds the institutions of every other Member State: under Article 5(1) of Regulation (EC) No 987/2009 they must accept it for as long as the issuing State has not withdrawn it or declared it invalid (EUR-Lex). A host institution that doubts the A1 does not decide the question itself: it goes back to the issuing institution, whose review is described under withdrawal below.

Binding on Institutions and Courts Until Withdrawn

The Court of Justice has extended the binding effect from host institutions to host courts and kept it in place where the conditions behind the certificate are disputed. In Fitzwilliam (C-202/97, 10 February 2000) it held the E 101 binding on the institutions of other Member States and required the issuer to re-examine, and where appropriate withdraw, a certificate when doubts are raised. In Herbosch Kiere (C-2/05, 26 January 2006) it held that the E 101 binds the host courts too, which may not scrutinise its validity.

A-Rosa (C-620/15, 27 April 2017) kept the effect even where the conditions clearly do not fall within the material scope. Alpenrind held the A1 binding until withdrawn, even after an Administrative Commission finding that it was wrongly issued. DRV Intertrans (C-410/21 and C-661/21, 2 March 2023) applied it while the issuer had provisionally suspended the certificate's effects.

Two Limits: Matters Outside Social Security and Fraud

The binding effect stops at social security: in Bouygues travaux publics (C-17/19, 14 May 2020) the Court held that the certificate binds host courts solely in that area.

Fraud is the second limit. Altun (C-359/16, Grand Chamber, 6 February 2018) lets a national court disregard E 101 certificates obtained or relied on fraudulently where the issuing institution fails to review them in the light of the evidence, with fair-trial safeguards. Vueling (C-370/17 and C-37/18, Grand Chamber, 2 April 2020) allows a fraud finding only after the procedure under Article 84a(3) of Regulation (EEC) No 1408/71 was promptly initiated and the issuer failed to review and decide within a reasonable time. DRV Intertrans adds that a criminal court may disregard the A1 after a reasonable period. In ONSS (C-421/23, 23 January 2025) the Court treated the dialogue and conciliation procedure as a compulsory precondition of a fraud finding and held that Regulation (EC) No 883/2004 applies even where host courts find A1 documents false. Since 1 November 2026, Article 1(2)(ea) of Regulation (EC) No 987/2009 defines fraud in the coordination rules.

How an A1 Is Withdrawn or Declared Invalid Today

Only the issuing State can withdraw an A1 or declare it invalid: a host institution that doubts it asks the issuing institution to review it, and the two follow the dialogue and conciliation procedure of Administrative Commission Decision No A1 of 12 June 2009. The procedure rests on Decision A1, Article 76(6) of Regulation (EC) No 883/2004 and Article 5 of Regulation (EC) No 987/2009, under which the issuer reconsiders the document and withdraws it if necessary.

The Dialogue and Conciliation Procedure under Decision A1

The procedure runs in two stages between the institutions, then before the Administrative Commission, and each step has its own deadline.

Where the dispute is about which legislation applies, Article 6 of Regulation (EC) No 987/2009 provides for provisional application of legislation while the institutions differ.

Own-Motion Withdrawal by the Issuing Institution

An issuing institution may also withdraw an A1 on its own review: in ZUS (C-422/22, 16 November 2023) the Court held that it does not first have to start the dialogue and conciliation procedure. Withdrawal ends the binding effect of Article 5(1) of Regulation (EC) No 987/2009.

What Changes for A1 Validity and Withdrawal from 2 November 2028

From 2 November 2028 Regulation (EU) 2026/2359 gives the doubt procedure statutory deadlines: the issuing institution withdraws or rectifies the A1 within 30 working days where it finds an error, and that withdrawal or rectification has retroactive effect (Article 19a(2) of Regulation (EC) No 987/2009). Regulation (EU) 2026/2359 of 7 October 2026 (EUR-Lex) was published in the Official Journal on 27 October 2026 and entered into force on 1 November 2026, but these rules apply only from 2 November 2028; until then Decision A1 and the case law above apply, as set out in the revision of Regulations 883/2004 and 987/2009.

Article 87b(4) of Regulation (EC) No 883/2004 keeps the old Article 12 for employed persons sent before 2 November 2028, so that date does not by itself end an A1 for such a posting. The 2028 rules apply in the EU, and their take-over by Norway, Iceland, Liechtenstein and Switzerland is pending as of 5 November 2026.

How to Keep an A1 Valid for the Whole Posting

Keep the end date on the A1 in step with the posting: check it when the A1 arrives, again whenever the plan changes, and well before the end date. Five steps do this.

1. Compare the period and conditions on the A1 with the planned work.
2. Count the posting on the 24-month social security clock, not on the labour-law clock.
3. Ask for an exception agreement under Article 16(1) of Regulation (EC) No 883/2004 before the end date where the work will run past 24 months.
4. Request the A1 in advance wherever possible, as Article 15(1) of Regulation (EC) No 987/2009 asks, and apply for an A1 certificate before the work starts.
5. Ask the institution that issues the A1 certificate to review the A1 when a host institution doubts it.

The A1 is one part of the obligations of a posting, and every obligation before, during and after it is listed in the posting compliance checklist.

Around A1 Validity: The Posting Period, the Labour-Law Clock and Penalties

A1 validity sits between four neighbouring rules that are explained on their own pages.

• The 24-month posting rule and its conditions: Article 12 of Regulation (EC) No 883/2004 and Decision No A2.
• The labour-law clock: long-term posting after 12 months, or 18 months on a motivated notification, under Article 3(1a) of Directive 96/71/EC, after which the worker stays posted.
• The fines: posting penalties for a missing A1 by country.
• The other judgments: posting of workers case law beyond the A1 rulings above.

Questions on A1 Validity

Four questions come up most often about how long an A1 lasts and what it is worth in the host State.

Does an A1 certificate expire?

Yes: an A1 is valid until the end date its issuing institution states on it (Article 19(2) of Regulation (EC) No 987/2009), which for a posted employee is at most 24 months (Article 12(1) of Regulation (EC) No 883/2004). The issuing State can end it earlier by withdrawing it.

Can an A1 be extended beyond 24 months?

Not under the posting rule: Article 12 of Regulation (EC) No 883/2004 stops at 24 months, and only an exception agreement under Article 16(1) between the States concerned keeps the home legislation longer. For postings between the UK and the EU, Article SSC.11 of the TCA Protocol also stops at 24 months.

Does an A1 issued before 2 November 2028 stay valid after that date?

Yes, in the EU, for a person sent before that date: Article 87b(4) of Regulation (EC) No 883/2004 keeps the old Article 12 for employed persons sent before 2 November 2028. The take-over of the 2028 rules by Norway, Iceland, Liechtenstein and Switzerland is pending as of 5 November 2026.

Can a host country ignore a valid A1?

No: the institutions of other Member States must accept the A1 until the issuing State withdraws it or declares it invalid (Article 5(1) of Regulation (EC) No 987/2009), and the Court of Justice extends this to host courts, which may set it aside only for fraud after the dialogue and conciliation procedure.