UK Post Office Horizon payment system

Horizon is a controversial software accounting system developed by Fujitsu and used by the UK Post Office since 1999. The use of Horizon resulted in what many people consider the UK's largest miscarriage of justice with sub-postmasters unfairly accused, convicted and imprisoned on charges of theft, false accounting.

In December 2019, UK High Court judge Peter Fraser ruled (pdf) Horizon was not 'remotely robust', contained 'bugs, errors and defects', and constituted a 'material risk' that shortfalls in branch accounts were caused by the system. The ruling saw the Post Office agreeing to settle with 555 claimants, having accepted that it had previously 'got things wrong in [its] dealings with a number of postmasters'. It was to pay GBP 58m in damages.

In February 2020, the UK government announced it would hold an official independent inquiry into the scandal, upgraded in June 2021 to a public inquiry. The government later offered Post Office workers with wrongful convictions for theft and false accounting GBP 600,000 each in compensation, and in January 2024 it said it would introduce legislation to exonerate wrongfully convicted. 

Plagued by poor transparency by the Post Office, Fujitsu and their advisors, the long-running saga has involved the obfuscation, blocking and delayal of mediation and litigation procedures, amongst other legal and reputational defensive tactics.