Changes made by Council Directive 2004/66/EC of 26 April 2004 adapting Directives 1999/45/EC, 2002/83/EC, 2003/37/EC and 2003/59/EC of the European Parliament and of the Council and Council Directives 77/388/EEC, 91/414/EEC, 96/26/EC, 2003/48/EC and 2003/49/EC, in the fields of free movement of goods, freedom to provide services, agriculture, transport policy and taxation, by reason of the accession of the Czech Republic, Estonia, Cyprus, Latvia, Lithuania, Hungary, Malta, Poland, Slovenia and Slovakia
EU Directive 2004/66
The legislation Council Directive 2004/66/EC of 26 April 2004 adapting Directives 1999/45/EC, 2002/83/EC, 2003/37/EC and 2003/59/EC of the European Parliament and of the Council and Council Directives 77/388/EEC, 91/414/EEC, 96/26/EC, 2003/48/EC and 2003/49/EC, in the fields of free movement of goods, freedom to provide services, agriculture, transport policy and taxation, by reason of the accession of the Czech Republic, Estonia, Cyprus, Latvia, Lithuania, Hungary, Malta, Poland, Slovenia and Slovakia changes, newest first. Choose one to see each change.
From legislation.gov.uk's record of changes, the official one: see it there.