Willis is a Senior Internal Auditor, National Treasury. He has participated in drafting a number of laws, regulations and guidelines, including the Constitution of Kenya 2010, the Public Finance Management Act, 2012, the Public Procurement and Disposal Acts (2005 & 2015), the CRA Act, the Controller of Budget Bill, the Public Audit Act, and the Internal Audit Bill, to mention a few. He is currently, the Treasurer at the Institute of Internal Auditors.