The CIO of Her Majesty's Revenue and Customs (HMRC) Phil Pavitt is leaving the role to join insurance giant Aviva plc early next year as global director of IT transformation.
HMRC's new CIO is Mark Hall, who has worked as deputy CIO at the department for two years and was director of IT services for three years before that.
A HMRC spokesperson said told ZDNet: "Having completed a number of major transformations at HMRC, Phil indicated that he wished to return to his private sector career."
CIO of the HMRC is one of the biggest jobs in public sector IT: the HMRC annual budget for IT was £840m in 2010, making it the third largest in government.
It relies on an expansive IT infrastructure, which, in 2010, included 650 major tax and benefit systems, 2,500 databases hosted on 6,300 servers in nine datacentres. HMRC also had 90,000 desktops and 9,000 laptops under its remit.
In 2011 HMRC revealed that through a programme known as Aurora, it aimed to cut IT costs to the tune of £161m per year by shutting down unnecessary IT systems and applications and moving applications onto new platforms.
Pavitt joined HMRC as CIO in 2009 after working as CIO at Transport for London where he was able to help reduce their IT spending by £400m.
Pavitt has been ranked as one of the top CIOs in the UK on several occasions, appearing on TechRepublic’s CIO50 list in 2008, 2009 and 2010.