Flag 4 Records reflect the number of individuals that register with a General Practitioner (GP) in England and Wales and whose previous address was outside the UK and who have spent more than three months abroad.


The Patient Registration Data System (PRDS), managed by the National Health Service (NHS), holds records of all patients registered with GPs in England and Wales (data are not available for Scotland). When individuals whose previous address was outside the UK and who have spent more than three months abroad register with a local GP, they are attributed a specific code (Flag 4). In theory, because all migrants are allowed to register with the local GP, regardless of their age and employment status, this source could provide a comprehensive coverage of immigration flows. For example, unlike other administrative sources, migrant children are likely to be recorded.


There is no indication of the delay between arrival and registration.

There is no information on patients who have left the UK.

Some migrants may not register for GP services at all – particularly short-term and/or younger economic migrants, especially healthy males.

The Flag 4 code is not retained once a patient moves within the UK and registers with a new GP (a relatively frequent occurrence even for short-distance moves). As the Flag 4 estimates are based on a mid-year ‘snapshot’ of the PRDS files, if this internal migration occurs within the year of first registration, i.e. before the following mid-year snapshot, the in-migration will not be recorded.

Age and gender are recorded, but information on nationality and country of birth is not systematically collected.

Flag 4 GP Registrations by local authority

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This Migration Observatory is kindly supported by the following organisations.

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