Linguistic Assessment Board test (PLAB), which has to be sat by non-European Union overseas doctors before they may practice medicine in the UK as a registered doctor. A registered practitioner found to have committed some offences can be removed from ("struck off") the Medical Register. Licensing and revalidating doctors in the UK The GMC is now empowered to license and regularly revalidate the practice of doctors in the UK. When the licensing scheme was introduced in 2009, 13,500 (6.1%) of registered doctors chose not to be licensed. Unlicensed but registered doctors are likely to be non-practising lecturers, managers, or practising overseas, or retired. Whereas all registered doctors in the UK were offered a one-off automatic practise licence in November 2009, since December 2012 no licence will be automatically revalidated, but will be subject to a revalidation process every five years. No doctor may now be registered for the first time without also being issued a licence to practice, although a licensed doctor may give up their licence if they choose. No unlicensed but registered doctor in the UK is subject to revalidation. However, unlicensed but registered doctors in the UK are still subject to fitness-to-practice proceedings, and required to follow the GMC's good medical practice guidance. Setting standards of good medical practice The GMC sets standards of professional and ethical conduct that doctors in the UK are required to follow. The main guidance that the GMC provides for doctors is called Good Medical Practice. This outlines the standard of professional conduct that the public expects from its doctors and provides principles that underpin the GMC's fitness-to-practise decisions. Originally written in 1995, a revised edition came into force in November 2006, and another with effect from 22 April 2013. The content of Good Medical Practice has been rearranged into four domains of duties. Their most significant change is the replacement of a duty to, "Act without delay if you have good reason to believe that you or a colleague may be putting patients at risk," to a new duty to, "Take prompt action if you think that patient safety, dignity or comfort is being compromised". Alongside the guidance booklet are a range of explanatory guidelines, including a new one about the use of social media. The GMC also provides additional guidance for doctors on specific ethical topics, such as treating patients under the age of 18, end-of-life care, and conflicts of