2. External calculation tool developers shall submit an application to a conformity assessment body as referred to in Article 14 that shall assess the compliance of the external calculation tool with the requirements laid down in Articles 3 to 9. In the case of a positive assessment, the conformity assessment body shall issue a certificate of the conformity of the external calculation tool with this Regulation. The certificate shall be valid for two years. In the case of a negative assessment, the conformity assessment body shall provide the reasons for the negative assessment to the applicant.