This certificate is conclusive evidence of your marriage but not of your identity. Some entities e.g. Passport Office & RTA require you to produce a registered copy of your Marriage Certificate. This is obtained from NSW Registry of Births, Deaths and Marriages $51 non urgent or $75 for urgent
You will be provided with an Application for a Marriage Certificate form in your package, or it can be downloaded from www.bdm.nsw.gov.au select ‘Forms, Fees & Turnaround’ then in ‘Marriage’ section select Marriage Certificate application.