Post Office chief executive Nick Read will step down from the role in March next year, the company said on Wednesday.
Mr Read described it as a "great privilege" to have worked as Post Office chief executive in an "extraordinarily challenging time for the business and for postmasters".
Mr Read had temporarily stepped back from the role in July to prepare for the next stage of the Horizon scandal inquiry.
The inquiry was called amid a widely-publicised scandal that the Post Office had used faulty accounting software to convict sub-postmasters on trumped up theft allegations, in what has been dubbed one of the largest miscarriages of justice in British legal history.
Following the announcement that he is stepping down from his role, Mr Read said: "It has been a great privilege to work with colleagues and postmasters during the past five years in what has been an extraordinarily challenging time for the business and for postmasters.
"There remains much to be done for this great UK institution but the journey to reset the relationship with postmasters is well under way and our work to support justice and redress for postmasters will continue."
Mr Read took on the chief executive position in 2019, succeeding former boss Paula Vennells, who this year forfeited her CBE following public anger over her handling of the Horizon crisis.
More than 700 subpostmasters were prosecuted by the Post Office and given criminal convictions between 1999 and 2015, as Fujitsu’s faulty Horizon IT system made it appear as though money was missing at their branches.
It comes after the Government announced that wrongly accused subpostmasters will be given an opportunity to have their cases re-assessed as part of an independent process alongside the Horizon inquiry.
His decision to step down in March next year comes during the continuing fallout from the Horizon scandal - which included MPs expressing a lack of confidence in his leadership at the business and trade committee in February.
Mr Read was also "exonerated of all misconduct allegations" following a report into his behaviour earlier this year.
The report came after he denied a claim made by former chairman of the Post Office Henry Staunton that he had tried to resign because of pay.
Lead campaigner and former subpostmaster Sir Alan Bates said Mr Read "hasn't achieved anything" during his time as chief executive.
Reacting to his decision to step down Sir Alan told the PA news agency: "Do you know, I predicted that.
"It's funny that because when I knew he'd taken seven weeks' leave - in theory to prepare for the inquiry - I thought he'd taken seven weeks off to find a new job.
"Honestly, that was my first thought."
Asked for reflections on Mr Read's five-year tenure, Sir Alan said: "Well, he really hasn't achieved anything, has he?
"He certainly hasn't done anything for the victims in all of this.
"I mean, I'm lost for words."
