STATUTORY CERTIFICATE: means a certificate which is required by a statute, considering the law of the country and based on expectation
MANDATORY CERTIFICATE: is a certificate required by the IMO Conventions. It is required for International Trading. (this ensure to improve the safety and security of international shipping and to prevent marine pollution from ships)
OBLIGATORY CERTIFICATE: is a certificate required by a particular state, therefore this certificate is required only by ships trading with that country.
Difference: while statutory is an expected certificate generally, mandatory certificates are the expected certificates that is recommended in the international operation and Obligatory is for the local operations in the same country.