What has become known as the ‘Horizon IT Scandal’ involves a dispute, between Post Office and a group of Postmasters, which took place over many years. It primarily concerned the reliability of the Horizon computer system used in post offices and issues related to Postmasters’ contracts and the culture of Post Office at the time.

The dispute culminated in civil litigation at the High Court, which concluded after a jointly agreed settlement in 2019. Several months later, in 2020, appeals of criminal cases in which Post Office had acted as prosecutor began through the criminal courts.

We are sincerely sorry for past events and recognise both the impact on individual lives and the length of time many victims have waited for justice. Providing compensation is a priority for us and we have already offered over £130m and continue to take determined action to reform our business.

An independent public Inquiry into the Horizon IT scandal was established in September 2020. Following a request from its Chair, Sir Wyn Williams, it became a statutory inquiry in June 2021. Post Office is fully participating to assist its work.

Group Litigation: 2016 – 2019

In April 2016, a High Court claim was issued against the Post Office by a group of Postmasters. A Group Litigation Order (GLO), a process for managing claims by people with similar or shared grievances, was issued by the Court in March 2017. This was the culmination of a long-running dispute primarily about the reliability of Post Office’s computer system Horizon and the legal meaning of Postmasters’ contracts.

Around 555 claimants joined the GLO. The litigation was complex and the Court ordered that the case would be heard as a number of trials. Two were held before a settlement of the case was jointly agreed in December 2019:

  • The Common Issues Judgment in March 2019 determined the legal construction of the contract between Post Office and Postmasters. It implied some new terms, most of which are additional obligations for Post Office, with a small number that also apply to Postmasters.
  • The Horizon Issues Judgment in December 2019 related to generic technical matters about the computer system since the original version was introduced in 1999. The Judgment found deficiencies in previous versions of the Horizon system, including that the potential for bugs to affect branch balances was greater than Post Office had believed. The current version of Horizon was found by both independent experts in the case, as well as the Court, to be robust, relative to comparable systems.

Individual claimants’ cases were not determined in the Group Litigation because a settlement was agreed before further trials took place to do so.

Mediation and settlement

A joint statement was released by both parties on 11 December 2019, that they had reached comprehensive resolution to the litigation.

The settlement was achieved through independent mediation, conducted through two mediator Queen’s Counsels (QCs). The agreement was informed by both the Common Issues Judgment and the Horizon Issues Judgment, with the latter provided by the Court under embargo on 28 November 2019.

The settlement deed was published by Post Office on 5 August 2020 under the Freedom of Information Act and can be found here. It included a global payment of £57.75 million, with individual payments for claimants to be decided by their legal representatives.

Whilst the settlement was jointly agreed in good faith as fair and appropriate in all the circumstances, subsequent media reports revealed that around £46 million of the £57.75 million global payment was directed to the claimants’ funders and legal advisors. We urged the Government to address this unfairness.

On 30 June 2022 Government announced a planned compensation package for GLO claimants and we welcome this action to ensure fair and final compensation. Further more recent information from Government can be found here: Compensation scheme for Group Litigation Order case postmasters - GOV.UK (


Post Office ceased private prosecutions related to Horizon in 2015. Appeals of cases in which Post Office acted as prosecutor began in 2020 with referrals by the Criminal Cases Review Commission (CCRC). These referrals followed the ‘Horizon Issues’ judgment in the Group Litigation. The appeals involve convictions for offences such as false accounting and theft.

As part of an extensive post-conviction disclosure exercise Post Office identified a total of 700 convictions in cases it prosecuted between 1999 and 2015 in which Horizon computer evidence might have featured (in some cases alongside other evidence).

The post-conviction disclosure exercise, by external criminal law specialists Peters & Peters, was established in January 2020. More than 60 million documents have been examined and thousands of physical and electronic sources have been interrogated to identify and disclose all material which might affect the safety of convictions. In addition, Peters & Peters liaised with a number of third parties including Fujitsu Services Limited, Royal Mail and its parent company International Distribution Services, the Courts, the Criminal Cases Review Commission and approximately 50 law firms and agents historically instructed by Post Office to obtain material relevant to the convictions.

 There is more information about appeals and compensation here.

*Page updated 13 December 2023