Most licensed doctors have a formal connection with one organisation, known as the 'prescribed connection'. This organisation is called your 'designated body'. It will provide you with a regular appraisal and help you with revalidation. A senior doctor in your designated body (often the medical director or equivalent) called the 'responsible officer' will make a recommendation to the GMC about you, usually every five years, that you are up to date, fit to practise and should be revalidated.
There is a clear set of rules that determines which designated body you are connected to. For most doctors, it is quite straightforward. For others, the prescribed connection is not as clear. Work is being done to support these doctors in finding their designated body. The GMC is asking doctors to confirm their designated body through their GMC On-line account.
The GMC have developed an on-line tool to help you check your designated body.
Alternatively, follow this link to an algorithm diagram (PDF) to check your designated body. When using the algorithm, reading from top left, the first green box you encounter determines where you will find your designated body, regardless of whether or not any of the subsequent boxes apply to you as well.