Who covers losses?

Richard Trinder, subpostmaster of three branches in Yorkshire and Derbyshire, and member of the Voice of the Subpostmasters campaign group, said that he lost hundreds of pounds in wages during the downtime. He asked: “Will the Post Office and Fujitsu compensate us for this?”

He also said business is lost when partners and customers go elsewhere. “For example, if you are offering Amazon delivery collection and you are down, they will go elsewhere and might never come back.”

Mark Baker, a former subpostmaster and current CWU postmaster representative, added: “Will customers who are cut off when in the Post Office ever come back? They will probably use a different branch, which means the individual subpostmaster has lost business.”

Regarding customers leaving a branch when an outage hits, Calum Greenhow, CEO at the National Federation of Subpostmasters (NFSP), said: “The Post Office always says, ‘These customers will come back’, but this is not the case because we no longer have a monopoly on many of the products.

“We know there is a service-level agreement where the Post Office pays Fujitsu for extra work when required, but we would like to know if there is one where Fujitsu has to pay for Horizon outages,” he added.

Greenhow said the NFSP has asked the Post Office whether compensation will be given to subpostmasters for loss of earnings and was told the Post Office would investigate it.

There is no service-level agreement between the Post Office and subpostmasters in relation to Horizon availability.

Lost in transaction

Baker at the CWU raised fears over an expected increase in lost transactions and unexplained losses caused during the outage: “The big problem is if the system is cut off while a transaction is in transit, or in the subpostmaster’s stack, it might not be recovered.”

He added that a transaction could also be lost because it’s in a queue at the datacentre.

The Post Office scandal, widely recognised as one of the biggest miscarriages of justice in UK history, was triggered by subpostmasters being blamed for unexplained accounting shortfalls.

“We are going through a very dangerous period until a new system and support is brought in,” warned Baker.

He added that the Post Office needs to look at the entire architecture when replacing Horizon. “It needs to look at the front end, back end and all the bits in between. They also need to look at the robustness of the support mechanisms when there is an outage.”

Computer Weekly asked the Post Office whether it would compensate subpostmasters for losses incurred during the latest outage but had not received a response by the time this article was published.

Computer Weekly also asked whether the Post Office would take any additional measures during the next accounting period to ensure that unexplained losses caused by transaction failures during the outage are identified. It has not yet responded.

The Post Office did not confirm whether Fujitsu will face any financial penalties because of the outage and Fujitsu has not confirmed whether it has identified the cause of the outage.

Specialist investigation firm Kroll is currently reviewing the integrity of current Horizon system data and the processes used to identify discrepancies. The investigation followed a report by the Post Office scandal public inquiry, published in September 2024, which raised concerns about the current version of the controversial system.

Computer Weekly asked the Post Office whether Kroll will include the latest incident as part of its review of the Horizon system, but it did not answer.

The Post Office scandal was first exposed by Computer Weekly in 2009, revealing the stories of seven subpostmasters and the problems they suffered due to Horizon accounting software, which led to the most widespread miscarriage of justice in British history (see below timeline of Computer Weekly articles about the scandal since 2009).