UK Home Office sham marriage algorithm

Released: April 2019

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The UK Home Office is reported as having been using an algorithmic system to detect 'sham marriages' in which couples get married to avoid immigration law rather than because they have a genuine relationship. 

According to the The Bureau of Investigative Journalism (TBIJ), the Home Office introduced an automated system to detect sham marriages in March 2015 as part of a 'hostile environment' immigration policy. The current machine learning-based triage system was introduced in April 2019.

The system makes an initial assessment over whether their partnerships are genuine or designed to get around visa rules by dividing couples into 'red' and 'green' light categories. A red light referral can put a person’s immigration and visa status at risk, and may lead to legal action and deportation.

Lawyers and civil rights advocates warn the system is opaque, unaccountable, may discriminate according to nationality and the age gap between partners, and may be flawed and unfair due to an over-reliance on automated decision-making.

Nationality, age discrimination

The TBIJ discovered in April 2021 that an equality impact assessment (EIA) conducted by the Home Office revealed issues with the 'triage' process, including the possibility of 'indirect discrimination' due to potentially biased information that also includes the age gap between partners.

Legal charity Public Law Project (PLP) had previously reported that Bulgarians, Greeks, Romanians and Albanians have been more likely to have their marriages rated ‘Red’ than others, and are therefore more likely to be targeted for investigation. 

According to Joint Council for the Welfare of Immigrants legal policy director Chai Patel, 'Home Office data on past enforcement is likely to be biased because Home Office enforcement is biased against people of certain nationalities.'


The existence of the algorithm was revealed by documents obtained by the Public Law Project through a Freedom of Information request. The eight criteria taken into account by the system when a marriage is flagged for analysis revealed by the EIA uncovered by the TBIJ remains unknown as they were redacted by the Home Office.

Legal challenge

In March 2023, PLP announced it had launched a legal challenge against the system, arguing it could discriminate against people from certain countries. 

Operator: UK Home Office
Developer: UK Home Office

Country: UK

Sector: Govt - home/interior

Purpose: Detect sham marriages

Technology: Machine learning
Issue: Bias/discrimination - age, nationality

Transparency: Governance; Black box; Marketing

Page info
Type: System
Published: February 2023
Last updated: March 2023