The most common reason for requiring an official translation is for certificates and similar, or if the text needs to have legal equivalence, for example in a court case, or if the translation needs to have the same status as an original document, e.g. an annual report that is to be submitted to a foreign or Swedish public authority.
The title of official translator is individual and protected. An official translator is a translator who has undergone comprehensive testing by Kammarkollegiet (the Swedish Legal, Financial and Administrative Services Agency), which examines the translator’s abilities to translate three types of texts over the course of one day: one general, one financial and one legal. The test is then assessed by an expert, and the translator needs to pass all three sections in order to be able to title themselves official translator. Each official translator receives their own number and a stamp, which must be used on the documents that are officially translated.
In Sweden you become an official translator between Swedish and another language. In other words you can not become an official translator between English and French, for example, in Sweden. A new test must be taken if the translator wishes to become an official translator in additional language pairs. The translator takes a new test every five years in order to maintain their title.