This document is an excerpt from the EUR-Lex website
Accession negotiations with a candidate member country are only launched when EU governments, meeting in the European Council, have unanimously agreed upon accession.
Negotiations take place in intergovernmental conferences between the governments of the EU countries and that of the candidate country. They help candidate countries to prepare for EU membership as well as allow the EU to prepare itself for enlargement in terms of absorption capacity.
On a practical level, the body of EU legislation (the 'acquis') is divided into 35 chapters (by policy). The Council decides unanimously whether to open each chapter.
When negotiations on all chapters are completed, the terms and conditions - including possible safeguard clauses and transitional arrangements - are incorporated in an accession treaty. This treaty needs the European Parliament's consent and the Council's unanimous approval. All contracting states then ratify it in line with their own constitutional rules.