Missing last departures, 2022 to 2024

FOI reference: FOI-2026-3525

You asked

In your note "International migration research, progress update: April 2026", you write that: "Our current LTIM method for emigrating EU+ and non-EU+ visa holders (FALD) uses a final departure date within a visa or multiple visas valid dates. For most emigrants, a final departure is present in the data. Where it is not, we currently assume that the person left at the end of their visa."

The piece then lists the multiple reasons why someone might not have a final departure present in the data.

I would like to know – for the three years where data is available – a) how many and b) what proportion of people do not have a final departure recorded?

We said

Thank you for your request. 

To produce estimates of long-term international migration for EU+ and non-EU+ visa holders, we use Home Office Borders and Immigration (HOBI) data. These data link travel histories from an individual's travel in and out of the UK, visa data, and other sources in the Initial Status Analysis (ISA) system, with more information provided in the Home Office statistics on exit checks: user guide. As with all large complex data collections based in administrative data, the data received may not always be complete and fully accurate. Records might not link in the ISA system because of administrative errors resulting in missing some travel events. Coverage is not complete for all travel routes, particularly for train and maritime travel or travel through the Common Travel Area (CTA).

Our method to estimate migration for non-EU+ and EU+ visa holders can see all visas a person has, and uses first arrival and last departure dates, allowing for other travel in and out of the country in between. This "First Arrival, Last Departure" (FALD) method is developed to determine that someone has immigrated or emigrated for 12 months or more, and meets the definition of a long-term international migrant (more information is available in our Methods to produce provisional long-term international migration estimates methodology).

To estimate emigration for visa holders for EU+ and non-EU+ nationals, we identify previous long-term immigrants who have a last departure from the UK, and do not return for at least 12 months.

Our emigration estimates, for the vast part, include people for which HOBI data has a last departure, and a smaller proportion of people for whom the data do not capture a last departure. These numbers can be seen in Table 1 in the associated download.

 Reasons for these missing departures include:   

• the departure has not been matched to an arrival by the system 

• the person has emigrated via the Common Travel Area 

• the person has dual nationality and has used different documentation to enter and leave the UK 

• the person died while in the country 

The method makes assumptions about people's journeys. Where a last departure is missing in the HOBI data, we assume a departure has taken place at the end of a person's visa (or last visa if they have more than one). As we continuously improve our methods and learn more about the HOBI data, we have also found that in some instances, people who come to the end of their visa might still be in the UK, and our current method would incorrectly emigrate them. These people may have:   

• made an in-country visa application after their previous leave expired, and have permission to stay in the country via a process known as 3C leave (PDF, 250KB)

• overstayed their visa and have not applied for another visa

It is these two groups where our research is focused, as outlined in our latest International migration research progress update article. We are working to update our current methods related to 3C leave in our Long-term international migration (LTIM) bulletin published 21 May 2026, to avoid emigrating those who are in between visas.  

We have been working with the Home Office (HO) to identify indicators of 3C leave in administrative data, and to develop a method to account for overstayers in the LTIM emigration estimates. Determining who is an overstayer is challenging because we are trying to evaluate if a missing departure is because of missing data, being between visas (3C leave), or a genuine non-departure. 

We know numbers for more recent time periods of missing departures decrease over time, as we get more complete information. This can be seen in the attached table. Updates to emigration estimates based on HOBI are related to: 

• updated historical travel data in HOBI and improvements to the data matching process by HO 

• new travel data, particularly for the most recent arrivals who have not yet been in or out of the UK for 12 months or more 

• methodological changes

As part of our continuous improvement approach, we are working to include information on the number of missing departures in our Admin-based long-term international migration estimates QMI, published alongside future migration releases. 

If you need anything else, please do not hesitate to contact pop.info@ons.gov.uk.