Serco's UK and Europe boss has stepped down as the firm attempts to "refresh" its relationship with its biggest customer, the UK government.
Jeremy Stafford is to be replaced by Andrew White, the current UK and Europe chief operating officer, the firm said.
Serco is being investigated by the Serious Fraud Office after claims it had overcharged the government for electronic tags for criminals.
In July, Justice Secretary Chris Grayling said an audit had revealed a "significant anomaly in the billing practices" of both Serco and rival G4S.
Mr Grayling said that since 2005, the companies had in some cases been charging for tagging offenders who were in prison, had left the country or were dead.
Both companies have been banned from signing any new contracts until the Cabinet Office has completed a review into their working practices.
The government alerted the Serious Fraud Office to the alleged malpractice in September.
Serco, which has a global workforce of about 120,000, responded by promising to spin out its government work into a separate business that could be more closely monitored.