An independent investigation has found that software problems in the Post Office Horizon system led to cases of branch managers being overcharged.
A report from independent forensic accountants Second Sight into problems experienced with the Horizon computer system revealed that the Post Office itself identified a number of defects in the software used to record transactions at branches. The two software faults, in 2011 and 2012, led to shortfalls of £9,000 at 76 branches, according to the BBC.
In these particular instances the Post Office cancelled the losses and sub-postmasters were not held accountable.
The Fujitsu-built system is at the centre of controversy over allegedly problematic accounting which has resulted in legal battles with sub-postmasters who claim to have been wrongly accused of fraud. A number of sub-postmasters were prosecuted as a result of the accountancy problems, which saw thousands of pounds go missing, and in some cases were jailed.
An investigation into the problems was launched by Second Sight last year after being commissioned by the Post Office.
The Post Office has welcomed the main findings of the report, claiming it highlights that no "system wide problems" have been found in relation to the Horizon software.
"We commissioned this independent review to address concerns that have been raised about the Horizon system and we welcome the broad thrust of the interim findings,” Post Office chief executive Paula Vennells said.
"The Post Office is committed to supporting its people and improving the way we do so. The interim review makes clear that the Horizon computer system and its supporting processes function effectively across our network. As the review notes, it is used by around 68,000 people in more than 11,500 branches, successfully processing more than six million transactions every day.
“The review underlines our cause for confidence in the overall system.”
However Vennels said that the report does “raise questions about the training and support we have offered to some sub-postmasters”, and said that the Post Office would continue to work to address any problems experienced by sub-postmasters.