Summary

There are two main sources of official statistics for migration:

The Office for National Statistics’ (ONS) Long-term international migration statistics estimate the number of people entering and leaving the UK for 12 months or more. These statistics are published every six months with a five-month lag. They coincide with the publication of the Home Office’s quarterly Immigration System Statistics and the Department for Work and Pension’s National Insurance Numbers allocated to adult overseas nationals entering the UK.

The Home Office’s Migration Statistics Collection brings together all published Home Office documents relating to statistics on migration. The reports include statistics about small boat arrivals, immigration detention, visa applications and outcomes, settlement and citizenship.

Things to consider

As statistics on migration and the asylum system cover a range of complex issues, it is important to understand the specific definitions, strengths and limitations of the individual statistics output to ensure that these statistics are not used to make claims that the data cannot support.

Migration and asylum are different. The Home Office defines asylum as a status granted to applicants that recognises they have a well-founded fear of persecution in their country of origin or country of former habitual residence for reasons of race, religion, nationality, political opinion or membership in a particular social group. Migration, however, could be used to discuss any entry or exit to and from the country, including through regular visa schemes covered in ‘those with indefinite leave’, and small boats crossings, covered in ‘illegal migration’.

The majority of long-term migrants, the definition of which is recommended by the United Nations, arrive through the regular immigration system on an approved visa.

Due to its operational role in monitoring those who enter and exit the country, the Home Office holds a wealth of management information alongside the official statistics it produces. Occasionally, this management information is used in public statements. The Home Office has taken steps to publish this information where it is used to support understanding – for example, on the Illegal Migration Bill.

ONS has made progress on its international migration estimates through a planned programme of improvement, moving away from survey-based estimates to use of administrative data sources. Its approach now uses Home Office Borders and Immigration data for EU+ estimates as well as continued use for non-EU+ estimates, while for migration of British nationals ONS is using Department for Work and Pensions’ tax and benefits data (the Registration and Population Interaction Database known as RAPID), rather than the International Passenger Survey. This now means that ONS no longer relies on survey data for any part of its migration estimates and are instead using administrative data that enables it to produce estimates based on observed behaviours, rather than relying on what people say their future intentions while travelling through a port or airport.

These statistics often receive a lot of media coverage around the time of their publication.

What to look out for

It is important that users of migration statistics fully understand the terminology around the statistics and are clear when communicating this to others.

• Migration is the movement of people from one place to another and covers a wide range of people who are moving for different reasons. Long-term migration refers to people entering or leaving the UK for a period of at least 12 months (in line with the United Nations definition)
• Immigration refers to people coming into the UK and emigration is people leaving the UK.
• Net migration is immigration less emigration.

Statements should be clear on which groups of migrants they are referring to as different types of migration may have different drivers, trends and different interactions with services. For example, a person that comes to the UK to study will likely have different interactions to a person that arrived in the UK on a small boat.

Immigration is a reserved policy area in the UK. This means that the power to make laws, set policies, and manage systems regarding immigration, asylum, and visas lies solely with the UK Parliament at Westminster, rather than the devolved administrations in Scotland, Wales, or Northern Ireland.

For those speaking on behalf of government we encourage them to consider how a typical person is likely to understand what they say. Being clear on definitions and the evidence underpinning any such statements helps maintain public confidence in the statistics and the organisations that produce them. An example of this is in our letter from the Deputy Chair of the UK Statistics Authority Penny Young on claims made about asylum seeker destinations.

Wider support

Other than the official statistics and ad hoc publication that have been highlighted there are a number of organisations that produce research and analysis on migration.

• The Migration Observatory informs and debates on international migration and public policy. You can find briefing and commentary on topics such as the impact of migration on the UK population growth and the UK’s asylum backlog.
• The House of Commons Library includes a section on immigration where you can find research briefings on changes to legal migration rules for family and work visas in 2024 and the UK-Rwanda migration and economic development partnership.
• The Institute for Public Policy Research has a migration policy unit that works with organisations in the migrants’ rights sector to provide policy analysis and advise on issues relating to immigration and integration.
• The Centre for Research and Analysis for Migration is an economics research centre with a focus on migration and labour economics.
• Full Fact, a team of independent fact checkers and campaigners, have also written an explainer on the UK asylum backlog.

In November 2025 ONS published an explainer piece called What is international migration and how do we estimate it?

The Home Office publishes a user guide to immigration system statistics designed to be a useful reference document on the issues and classifications that are used in the production and presentation of the Home Office Immigration system statistics releases. The Office for National Statistics has also published a technical user guide, which provides more information on how they produce the official migration statistics.

Long-term international and internal migration estimates at local authority level for England, Wales, Scotland and Northern Ireland are produced by the Office for National Statistics (ONS), National Records of Scotland (NRS) and Northern Ireland Statistics and Research Agency (NISRA) for the purpose of producing population estimates.

You can read more about our work on ONS transformation of Long-Term International Migration Estimates and our previous statements concerning refugees and economic migrants.