The Treaty concerning the accession of the Czech Republic, Estonia, Cyprus, Latvia, Lithuania, Hungary, Malta, Poland, Slovenia and Slovakia to the European Union was signed in Athens on 16 April 2003. Depositary: the Government of the Italian Republic. Authentic texts, equally valid, in 21 languages including Irish, under Article 3. Ratification follows each party's constitutional requirements, with instruments deposited by 30 April 2004. It enters into force on 1 May 2004 if all instruments have been deposited. It is not the Treaty of Nice and not the Accession Treaty of 25 April 2005, by which Romania and Bulgaria later joined.

Article 1 makes the ten states members of the Union and parties to the Treaties on which it is founded, as amended. The conditions of admission and the adjustments are set out in the annexed Act, which forms an integral part. The rights, obligations and institutional powers in the founding Treaties apply in respect of this Treaty. Signature took place at the Stoa of Attalus, under the Greek Presidency of the Council.

The Act of Accession adjusts, among other things, Council voting weights and the number of representatives in the institutions, along the lines of the Treaty of Nice; qualified-majority thresholds are not transcribed here as a voting handbook. The new members take part in economic and monetary union from the date of accession as Member States with a derogation. They undertake, at the level of principle, the Community's agreements with third parties and accession to the European Economic Area, on the terms of the Act. Transitional annexes are not copied here.

All 25 states ratified. The institutions could adopt, before accession, the measures listed in the Act, with effect only on the date of entry into force. The Official Journal published the text in L 236 of 23 September 2003. The register source is an EUR-Lex collection landing page, not the instrument; the official text is CELEX 12003T/TXT.

Cover: the accession treaty signing ceremony in Athens; a period photograph, without restating the date. Wikimedia Commons, free licence.

Sources consulted: Treaty of Accession 2003; Treaty of Accession 2003 (EUR-Lex 12003T/TXT).