(24)To safeguard the mutual recognition of qualifications, certificates of qualification should be based on the competences necessary for the operation of craft. Member States should ensure that persons receiving certificates of qualification have the corresponding minimum levels of competence, verified following an appropriate assessment. Such assessments could take the form of an administrative examination, or could form part of approved training programmes carried out in accordance with common standards in order to ensure a comparable minimum level of competence in all Member States for various qualifications.