The inquiry, led by retired Judge Robert Nugent, enters its third phase this week and is expected to sit until Friday.
The commission of inquiry looking into the affairs of the South African Revenue Service (SARS) continues on Tuesday, 25 September 2018.
Amongst those expected to give evidence are officials at National Treasury.
Consulting firm Bain & Company, which was hired by former commissioner Tom Moyane to develop a new operating model at SARS, is also expected to give testimony this week.
It was paid R164 million for its services, however, senior officials claimed that all the company did was destabilise SARS and collapse highly efficient revenue collecting units.
The company appeared before the Nugent commission last month in which it blamed SARS for the model’s failure, and also said it had been used for a political agenda.
“There is a growing frustration within our firm that we did not recognise the possibility that we may have been used to further a political or personal agenda”, Bain said in a statement.
Tom Moyane, who is a Commissioner at SARS, was suspended by President Cyril Ramaphosa earlier this year, accusing him of bring the revenue service into disrepute. He was hired by then President Jacob Zuma in 2014.
On his relationship with Moyane, Finance Minister Nhlanhla Nene told the inquiry in August that he often had to call him to order due to his focus on the so-called “rogue unit”.
“There is no perfect relationship but there could be a professional relationship. In the period I worked with the commissioner (Moyane)‚ we had a number of issues to deal with and I reached a point where in some instances‚ I had to point out to the commissioner that he was paying too much attention to the so-called rogue unit rather than tax collection‚” Nene said.