Post Office Horizon Scandal

The Post Office Horizon scandal is one of the greatest miscarriages of justice in British history. Many hundreds of postal workers were wrongfully convicted of theft or fraud due to flaws in the Horizon IT system used by the Post Office.

What is Horizon?

Horizon is a type of software introduced by the Post Office in 1999 and developed by the company Fujitsu. It is used for activities like stocktaking and accounting. When it was first introduced in 1999, it was the biggest non-military IT project in Europe.

A Horizon computer terminal

The system was, and still is, used by Sub-postmasters and Sub-postmistresses to log sales and generate accounts. Sub-postmasters and Sub-postmistresses (referred to in this article from this point forwards as Sub-postmasters) are self-employed business owners, approved by Post Office Ltd, to run post office branches. They are not directly employed by Post Office but do have a contract with them. This centralised computer system replaced paper accounting.

The Horizon scandal

Problems in the Horizon system were reported immediately after roll-out. The system incorrectly reported accounting shortfalls, sometimes amounting to thousands of pounds.

When these unexplained errors were reported, the Sub-postmasters were blamed for the errors.

Under the Sub-postmasters’ contracts, any shortfalls were their responsibility to pay back. It was almost impossible to prove that these errors were the fault of the Horizon system for those impacted.

What did this mean for the Sub-postmasters?

Sub-postmasters were forced to pay back what the Horizon system indicated they owed, or face prosecution. The Post Office has its own criminal investigations force with the power to prosecute without the involvement of the police.

Many Sub-postmasters paid the shortfalls to avoid prosecution. In many cases, this led to bankruptcy, losing their businesses, and struggling financially.

Almost 1000 Sub-postmasters were prosecuted for theft and false accounting, among other crimes. Many innocent people were sent to prison or were forced to live with a criminal conviction.

The impact of these accusations, prosecutions and convictions destroyed the lives of many hundreds of people. Some took their own lives. Others died with criminal convictions before they could get justice.

Why did the scandal go on for so many years?

The Post Office used criminal and civil legal action against Sub-postmasters. Often this legal action would bankrupt the accused. Some convictions resulted in prison sentences.

It has been reported by  Computer Weekly, among others, that call centre staff were instructed to tell Sub-postmasters no-one else was experiencing problems.

Have the Sub-postmasters found justice?

Alan Bates, a Sub-postmaster impacted by the Horizon scandal, led a drive to find and link up victims. The victims formed the  Justice for Sub-postmasters Alliance. The alliance led a campaign for justice, supported by local MPs and journalists.

As MPs began to raise issues, the Post Office launched a review. It brought in external investigators Second Sight to produce a report, delivered in 2013. However, their work was stopped by the Post Office in 2015.

At this point, the Justice for Sub-postmasters Alliance started a group litigation order. This meant that 555 victims sued the Post Office together on the basis that the Horizon system was unreliable. This did not go to court until 2018.

After a prolonged battle, the claimants won and were awarded £58million in compensation. However, after legal fees, this compensation did little to support the Sub-postmasters who lost their livelihoods.

The result of the ruling did allow Sub-postmasters who had been falsely convicted of crimes to appeal against their convictions. This started a slow process of quashing convictions.

In 2024, a 4-part ITV drama, Mr Bates Vs the Post Office, drew public attention to the situation on a scale that had not been achieved throughout the 20 previous years. As a result of the increased public interest, in May 2024 the Government announced new legislation to exonerate the wrongly convicted postal workers. Hundreds of convictions were struck from the record and families of deceased victims were able to clear their loved ones’ names.

However as of 2025, most Sub-postmasters still have not had the full compensation they are owed.

Public Inquiry and the continued fight for justice

In 2021, a public inquiry was launched. Led by Sir Wyn Williams, it has revealed the scandal’s devastating human impact.

The inquiry concluded in December 2024 and Volume 1 of the final report was published in July 2025. It found that nearly 1,000 Sub-postmasters were wrongfully prosecuted based on flawed data from the Horizon IT system, leading to wrongful imprisonment, financial ruin and terrible personal suffering. At least 13 suicides were linked to the scandal. The inquiry also determined that Post Office and Fujitsu executives either knew, or should have known, about Horizon’s defects.

The second volume of the report, which has not yet been published, is expected to focus on systemic failures and accountability.

London’s Metropolitan Police is investigating the Post Office over potential offences including perverting the course of justice and perjury.

So far, no Post Office or Fujitsu employees have been held accountable.

Horizon and The Postal Museum

The Postal Museum is the recognised Place of Deposit for records of Post Office Limited (POL). We provided records to the Post Office Horizon IT Inquiry to support their investigation. 

We have been collecting material related to the Horizon IT system for many years, and we continue to document the events and impact of the Horizon scandal. In the future we will tell this story in our displays and through our programming, in collaboration with those directly affected.

We are partnering with the Post Office Horizon IT Inquiry on their Legacy Project. We will work closely with current and former Sub-postmasters to develop a lasting record within the museum, bearing witness to their experiences and documenting the legacy of the scandal.

“From the very beginning, the Inquiry has put human stories at the heart of its work. I want these stories of hardship, suffering but above all else resilience to be marked in history, and this is the purpose behind the Legacy Project. 

“We don’t know what the Legacy Project will look like yet, as it will rightly be shaped by those who have been directly affected by the scandal. But one thing is certain: it will ensure that the effects of the Horizon scandal cannot be erased” 

– Sir Wyn Williams, Chair of the Inquiry. 