Sir Iain McMillan spent twenty-three years with the TSB Group prior to joining the Confederation of British Industry (CBI) in 1993. He held the position of Director, CBI Scotland for nineteen years until his retirement in 2014. Sir Iain holds a number of Board positions in the business and charitable sectors. He is currently Chairman of SkillForce and the University of Strathclyde Business School Advisory Board, a Member of the Competition Appeal Tribunal, Honorary Patron and former Chairman of the Scottish North American Business Council (SNABC) and a Trustee of The Carnegie Trust for the Universities of Scotland. In 2009, Sir Iain was appointed Honorary Air Commodore of 602 (City of Glasgow) Squadron, Royal Auxiliary Air Force.
Other appointments have included Membership of the Boards of the Scottish Qualifications Authority, the Scottish Ambulance Service, the British American Business Council and the Teaching Awards Trust. Over the years, he has served on other Boards and public policy groups, including the Commission on Scottish Devolution (Calman Commission). He also chaired the Independent Commission for Competitive and Fair Taxation in Scotland. In 2003, Sir Iain was appointed CBE for services to the business community and lifelong learning in Scotland. In 2015, Sir Iain was knighted for services to the Scottish economy and in 2018 he was appointed as a Deputy Lieutenant of Stirling and Falkirk.