President Cyril Ramaphosa is appearing at the state capture inquiry on Wednesday.
The president is set to return to the inquiry on Thursday as well.
The inquiry said Ramaphosa is expected to give evidence and be questioned on matters falling within the terms of reference of the inquiry, including ANC matters and evidence related to his terms as president and deputy president.
Ramaphosa previously appeared before the inquiry in April and said members of the ANC had engaged in acts of state capture and corruption for a number of years.
