Visa
Many countries have a mechanism to allow the holder of a visa to apply to stay longer in that country. For example, in Denmark a visa holder can apply to the Danish Immigration Service for a Residence Permit after they have arrived in the Country. In the United Kingdom applications can be made to the Border and Immigration Agency. In certain circumstances, it is not possible for the holder of the visa to do this, either because the country does not have a mechanism to prolong visas or, most likely, because the holder of the visa is using a short stay visa to live in a country. In such cases, the holder often engages in what is known as a visa run; leaving the country for a short period in order to apply for a new visa prior to their return or so that they can be given a fresh permission to stay when they re-enter.