An application for a marketing authorisation for a medicinal product for human use, as well as all subsequent dossiers such as variations and renewals, must be submitted in the CTD format. This is described in Appendix 1 of the Royal Decree dated 14/12/2006 relating to medicines for human and veterinary use and in the appendix of the European directive 2001/83/EC EudraLex - Volume 1 - European Commission.
The CTD format includes 5 sections that are identical for all member states of the European Union. The exact structure of the format is described in part 2B of the Eudralex collection, published by the European Commission EudraLex - Volume 2 - European Commission.
In that volume you will find references to the European and international guidelines concerning the scientific contents of a file and also a "Question & Answer" document concerning the practical use of this format in the European Union.
Sections 2 to 5 are identical for the European Union, the United States and Japan. You will find more detailed information on the website of the ICH international discussion forum (International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human use) : http://www.ich.org.
Since 1 January 2019, all submissions for medicinal products for human use must comply with the eCTD (electronic Common Technical Document) format. More information can be found on the EMA’s eSubmission website.