Former Post Office boss Paula Vennells has forfeited her CBE for “bringing the honours system into disrepute”.
Ms Vennells received the honour in 2019 but was widely criticised amid the fallout from the Post Office scandal.
She had previously said she would give up the honour, amid a recent uproar about her handling of the Horizon IT scandal which led to the wrongful prosecution of hundreds of subpostmasters.
On Friday, the King officially stripped her of the gong.
It comes after the ITV drama Mr Bates vs The Post Office set the scene for a petition to be started, demanding Ms Vennells be stripped of her honour. More than 1.2 million people signed it.
In January she announced her intention to give up her CBE, saying: “I continue to support and focus on co-operating with the Inquiry and expect to be giving evidence in the coming months.
"I have so far maintained my silence as I considered it inappropriate to comment publicly while the Inquiry remains ongoing and before I have provided my oral evidence.
"I am, however, aware of the calls from subpostmasters and others to return my CBE.
"I have listened and I confirm that I return my CBE with immediate effect.
"I am truly sorry for the devastation caused to the sub-postmasters and their families, whose lives were torn apart by being wrongly accused and wrongly prosecuted as a result of the Horizon system.
"I now intend to continue to focus on assisting the Inquiry and will not make any further public comment until it has concluded."
MPs and victims of the scandal have for years called for Ms Vennells to be stripped of the rank, which has the full title Commander of the Most Excellent Order of the British Empire.
While an individual can signal they want to renounce their honour, the only person who can sign off on the forfeit is the monarch, following advice from the Forfeiture Committee - something Charles has now done, in Ms Vennells' case.
Before the former Post Office boss issued her statement last month, Downing Street had made it clear that Prime Minister Rishi Sunak would "strongly support" a review of whether she should hold onto the honour.
Ms Vennells was running the Post Office while it routinely denied there was a problem with the Horizon software.
Based on the data from the system, the Post Office prosecuted 736 sub-postmasters and sub-postmistresses between 2000 and 2014, or one per week on average.
As a result, following convictions for theft and false accounting, some were sent to prison; many others experienced financial collapse and have spoken of being shunned by their communities. Some have now passed away.
Campaigners have since won a legal struggle after 20 years, arguing that the computer system was broken, to have their cases reexamined.
The case, considered the country’s biggest miscarriage of justice, was brought back into the public eye when ITV aired its show.
An enquiry is currently ongoing and is scheduled to finish with recommendations for the future in September.
