Article 233
1. Invoices sent or made available by electronic means shall be accepted by Member States provided that the authenticity of the origin and the integrity of their content are guaranteed by one of the following methods: (a) by means of an advanced electronic signature within the meaning of point (2) of Article 2 of Directive 1999/93/EC of the European Parliament and of the Council of 13 December 1999 on a Community framework for electronic signatures ( 10 ) ; (b) by means of electronic data interchange (EDI), as defined in Article 2 of Commission Recommendation 1994/820/EC of 19 October 1994 relating to the legal aspects of electronic data interchange ( 11 ) , if the agreement relating to the exchange provides for the use of procedures guaranteeing the authenticity of the origin and integrity of the data. Invoices may, however, be sent or made available by other electronic means, subject to acceptance by the Member States concerned. 2. For the purposes of point (a) of the first subparagraph of paragraph 1, Member States may also ask for the advanced electronic signature to be based on a qualified certificate and created by a secure-signature-creation device, within the meaning of points (6) and (10) of Article 2 of Directive 1999/93/EC. 3. For the purposes of point (b) of the first subparagraph of paragraph 1, Member States may also, subject to conditions which they lay down, require that an additional summary document on paper be sent.