The team was quick to contact the subpostmaster to investigate the problem at his branch, which experts believe is the same type of error responsible for many unexplained accounting shortfalls in branches over the two decades since Horizon was introduced.
The Post Office’s response came after Computer Weekly published details of the problem.
This error is significant in relation to the Post Office Horizon scandal, which saw hundreds of subpostmasters wrongly blamed for accounting shortfalls in branches, because it appears to be a manifestation of an error highlighted by forensic accountants seven years ago.
A Computer Weekly investigation in 2009 revealed that subpostmasters, who run Post Office branches, were being blamed for unexplained financial losses, which they claimed were caused by errors made by the Horizon system. The Post Office denied this, and subpostmasters were subsequently prosecuted for theft and false accounting, with prison sentences, community service, criminal records and heavy fines among the injustices they suffered as a result.
This has become one of the biggest miscarriages of justice in UK history (see timeline below).
Transaction error
Late last month, Computer Weekly revealed a fault at a Post Office branch which occurred when a customer tried to withdraw money from their Nationwide Building Society account. The error saw the customer’s withdrawal transaction declined even though the system had debited his account.
The regular customer tried to withdraw £400, but when staff at the branch processed it, the screen said the transaction had been declined. The customer confirmed he had enough money in his account, so the staff tried again, but this time split the transaction into smaller amounts. A transaction for £300 was also declined and the receipt showed this was because the customer had exceeded his daily limit, even though the previous transaction had been declined and nothing had been withdrawn that day. After a third attempt, the Post Office staff gave up.
This transaction error was spotted by the branch subpostmaster, Mark Baker, who is branch secretary at the Communications Workers Union.
After being told about the problem, the customer visited a Nationwide branch where he was given the money and told that the building society would recover the money from the Post Office. The way Nationwide dealt with the problem suggested it had happened before.
Ron Warmington, head of Second Sight, which investigated Horizon errors for the Post Office, strongly suspected that a substantial proportion of the historical shortfalls would be attributable to this type of error, which he described as a one-sided transaction.
When two systems are running together – these being Horizon and the Link inter-bank payment system in the case of the incident revealed to Computer Weekly – four things can happen: both work, neither works, or one works but the other doesn’t and vice versa.
Impressive response
Baker said that after writing to the Post Office’s head of IT about the error, a dedicated banking team at the Post Office contacted him and visited his branch to investigate.
In the past, the Post Office did not properly investigate why shortfalls were occurring, but since losing a High Court case in December, when it was criticised by judge Peter Fraser, the Post Office committed to improving. The judge described the Post Office’s denial that computer errors could cause shortfalls as being like a “21st century equivalent of maintaining that the Earth is flat”.
Baker said the Post Office’s reaction, in this latest case, was “impressive”, and although it remained to be seen how long it would take to resolve this and what answers it might come up with, he couldn’t fault its reaction to what could be a serious problem.
“I suspect [the Post Office] knows who I am and has been briefed. The last thing it wants is for someone like me to have an IT problem”
Mark Baker, subpostmaster and union representative
In his role as a subpostmaster and union representative, Baker has been a vocal campaigner for justice for subpostmasters affected by Horizon errors. He was described by Fraser in his High Court judgment as “redoubtable”.
Baker said this could have influenced the Post Office’s response to his problem. “I suspect strongly they know who I am and have been briefed. The last thing they want is for someone like me to have an IT problem,” he said.
A Post Office spokesperson said the issue was being investigated by a dedicated team: “Post Office has commenced a detailed examination of records from all the systems that formed part of this transaction. This work is ongoing and we are directly liaising with the subpostmaster to help determine the root cause of the issue he has reported.”
The spokesperson added that the team “focuses on the investigation and remediation of issues such as this”.
Baker added that the Post Office’s reaction could be related to its important relationship with banks. “It could also realise that a problem like this could undermine the credulity of using Post Office in place of banks because the IT is not up to the job on occasion,” he said.
The Post Office is seen as an increasingly important alternative to bank branches as more are closed down, particularly in rural areas. As bank branch closures gather pace, transaction volumes at Post Offices are expected to increase. The latest figures show that cash deposits by business and personal customers at Post Offices totalled £2bn in September 2020.
More than 30 banks and building societies are part of the Post Office’s Banking Framework, which enables customers to withdraw or deposit cash at any Post Office branch. Customers can pay in cash and cheques, withdraw money and check their account balance.
The Post Office spokesperson added that it had a specialist team that looks after all things related to banking.
Log of errors
The fact that the issue is being investigated so thoroughly is evidence of the challenges faced by subpostmasters. This type of error has been known about for some time, but subpostmasters are still in the dark about it.
The Post Office said it was attempting to address this through the launch of a log of errors for postmasters of the known current Horizon or transaction issues that it is aware of. “Every issue will be included unless it is specific to an individual branch and the log will be updated regularly,” it said. “If there is an issue with a significant potential operational impact, then branches will be advised, as we do now, in a separate communication.”
The Post Office has faced criticism for not being open with subpostmasters about potential errors. It has a log of thousands of known errors, which it denied existed until it was forced to reveal it during the legal battle with subpostmasters.
Asked about the new log launched by the Post Office, Baker said: “It’s simply not the sort of log that subpostmasters are looking for. We are looking for technical breakdowns. We are all aware that they misprogram some of our transactions, which are transactional errors in the front-end software. What we are looking for is the technical errors that occur in the back office that can affect our balance.
“The Post Office needs to be publishing the ‘known errors log’. If an error has been found and a fix is being sorted, it needs to be flagged up. For example, the error I have identified should be on the log now and subpostmasters should be sent warnings in real time.”
Timeline of the Post Office Horizon case since Computer Weekly first reported on it in 2009
May 2009: Bankruptcy, prosecution and disrupted livelihoods – postmasters tell their story.
September 2009: Postmasters form action group after accounts shortfall.
March 2020: Labour MP Karl Turner tells Computer Weekly that the Post Office Horizon scandal is the most grotesque version of predatory capitalism he has ever seen.
