The Home Office publishes data collected in the process of managing entries into the UK and other changes of the legal status of persons subject to immigration control (i.e. non EEA/Swiss nationals entering the UK).
The Home Office, through the UK Border Agency, collects detailed information on entries into the UK by persons subject to immigration control. There are two main types of entry data: entry clearance visas issued, and passenger entries recorded. For each entry or visa, data are gathered on the legal basis for entry (including Tiers of the Points-Based System), as well as information on the individual entrant (such as nationality). Visa data are complete counts of all visas issues; passenger entries for particular categories of migrants are based on projections from a sample of the full set of landing cards filled out upon arrival at ports of entry. Administrative data also tracks subsequent changes of legal status for persons subject immigration control, such as applications for asylum, settlement, citizenship, or extensions of leave to remain. Enforcement procedures such as denial of entry, detention under Immigration Act powers, and removals appear in administrative data as well.
Data on departures are not available, meaning that administrative data can only be used for immigration, not net migration.
Entry clearance visa and passenger entries include people who do not qualify as a long-term international migrant by government definition, because they do not meet the one year length-of-stay requirement.
Visa data includes some unknown number of people who never arrive in the UK.
Citizens of EEA countries (and Switzerland) are not counted in administrative data (except on naturalisations).