Is the CEP mandatory for marketing a substance in EU countries?

Answer:

No. The CEP is an official procedure implemented by EU Directive; it is optional and not a mandatory requirement in Europe for marketing substances. Nevertheless, it is the preferred option to demonstrate that a substance used in the preparation of medicinal products comply with the European Pharmacopoeia specifications according to the Note for Guidance on summary requirements for active substances in the quality part of the dossier (CPMP/QWP/297/97 Rev 1; EMEA/CVMP/1069/02).
It is also the preferred option to demonstrate compliance with the requirements concerning TSE risk (general chapter 5.2.8 of Ph.Eur= EMEA NfG 410/01; minimising the risk of transmitting animal spongiform encephalopathy agents via medicinal products)