Resignation as deputy First Minister
replaced McGuinness as Sinn Féin's leader in the Northern Ireland Assembly in January 2017
In November 2016, a scandal came to light surrounding the Renewable Heat Incentive (or "Cash for Ash"), an energy incentive championed by Arlene Foster when she was Minister for Enterprise, Trade, and Incentives in 2012. The incentive would cost the Northern Ireland Executive £480m over 20 years, and was marred by allegations of fraud, which were not acknowledged or acted upon by Foster or the DUP. McGuinness and others in Sinn Féin called for Foster (now First Minister) to step aside to allow for independent inquiries, but Foster refused. Foster made a statement before the Assembly on 19 December without McGuinness' approval (as required under the power-sharing agreement), resulting in Sinn Féin and the opposition parties all walking out of the Assembly.
Sinn Féin President Gerry Adams indicated on 8 January 2017 that McGuinness could resign, thus vacating both his and Foster's offices, if Foster did not agree to temporarily step aside to allow an independent inquiry. McGuinness resigned the following day; in his statements to the press, he said "Today is the right time to call a halt to the DUP's arrogance", and said that Foster had a "clear conflict of interest" in the affair. Another reason cited for his resignation was the decision by DUP Minister for Communities Paul Givan to remove £50,000 in funding from the Liofa Gaeltacht Bursary scheme, a yearly programme that allowed 100 school-age children to travel to the Donegal Gaeltacht to learn the Irish language. Sinn Féin refused to nominate a successor to McGuinness before 16 January, resulting in the Secretary of State for Northern Ireland, James Brokenshire, calling for new elections scheduled for 2 March. McGuinness subsequently announced that he would not run for re-election, due to ill health.