In this Practice Note, the terms ‘leave to enter/remain’ and ‘permission to enter/stay’ are used interchangeably. The word ‘permission’ replaces ‘leave’ in the Immigration Rules for simplified routes, but the former term is still used in other categories of stay and the relevant legislation. This Practice Note explains what happens to a person’s leave to enter or remain in the UK when they: • travel outside the UK, the Channel Islands, the Isle of Man and Ireland. This geographical area is known as the Common Travel Area (CTA). For information on immigration regulations within the CTA, see Practice Note: The Common Travel Area • make an in-country application to 'vary' their leave • lodge an in-country appeal • make an in-country application for administrative review, or • withdraw an in-country variation of leave application before it is determined Where a person already has leave to enter or remain, any application to extend, reduce or otherwise alter this leave is termed under the Immigration rules as an application to vary