The commission was set up by President Cyril Ramaphosa in May after he suspended SARS Commissioner Tom Moyane, who is also facing a disciplinary hearing.
Headed by former Judge Robert Nugent, the commission is expected to conclude its first round of hearings on Friday.
Gordhan, who fell out publicly with Moyane, is due to testify at 2.30pm.
The inquiry is probing whether Sars took appropriate steps to address revenue collection shortfalls in recent years, as well as the impact the running of the revenue service had on its public image.
– African News Agency