A two-step process
A certified translation is one where the translator attaches a statement, produced in front of a notary, stating that the translation is true, accurate, and correct "to the best of my knowledge and ability".
This is often required when translating
. Birth, adoption, marriage or death certificates
. Academic degrees or diplomas
. Naturalization or immigration documents
. International brand names, copyrights or patents
The statement is notarized to confirm the identity of the person signing the statement.
This is sufficient for most translations inside the country, but translations being sent abroad need an 'Apostille' affixed by the Competent Authorities.
Once a document has been translated the notarization is usually quite quick and should not take more than 1 to 2 hours. The time for the Apostille may take another day, so leave yourself enough time if you expect you will need these services.
Both these processes are charged separately from the translation itself.