The DUP leader Arlene Foster is set to appear in front of the inquiry into the Renewable Heat Incentive scheme next month.
The former first minister and DUP special adviser Andrew Crawford will give evidence from Wednesday April 11 until Friday April 13.
Mrs Foster was Enterprise Minister at the time the RHI scheme was launched in November 2012.
The botched green energy scheme was supposed to encourage businesses to switch to a more environmentally friendly heating system.
But a lack of proper costs controls left it open to abuse, with some applicants able to make money by burning more fuel than needed.
The failure sparked a political crisis at Stormont when the then Deputy First Minister Martin McGuinness resigned, effectively collapsing the power-sharing Assembly.