Bain has "clarified" that Vittorio Massone remains a partner at the Boston-based consultancy, but will no longer run its day-to-day operations.

In a statement on Sunday, Bain — which was contracted by the SA Revenue Service (Sars) to design and implement its restructuring — said that Massone had stepped down as managing partner.

On Monday, it said Massone was focusing his time on co-operating with the commission of inquiry into governance at Sars and had stepped aside from running the South African office.

"We have requested Tiaan Moolman to take over day-to-day operations as interim managing partner. It has been known to our clients for some time that Massone would rotate out of his current role in December to take on another senior role within the firm," Bain said in a statement on Monday.

"This rotation typically occurs each 5-7 years and Massone has already completed almost nine years in his current role."

Bain has become the latest multinational to be embroiled in state capture: it was contracted, allegedly via an irregular tender process, to overhaul the structure of Sars under suspended commissioner Tom Moyane when he took over in 2014.

The commission of inquiry into governance and administration at Sars, chaired by retired judge Robert Nugent, has heard how the increase in VAT for the first time in two decades — which has hit the economy and the poor hard — was necessary partly due to the revenue shortfall of R50bn by Sars in 2017-2018.

The Nugent inquiry has heard evidence from dozens of former and current Sars officials indicating that the Bain restructuring resulted in the depleted capacity at Sars, which led to the revenue shortfall.

The Bain restructuring at Sars had neutralised key units in the organisation such as enforcement, the large business centre, litigation and compliance. The consultancy only conducted 33 interviews over six days to conclude the work on restructuring the complex tax agency, which took two decades to build from scratch. Those interviewed were handpicked by Moyane.

Business Day understands that Massone had met former president Jacob Zuma twice at his private residence at Nkandla in 2013 and 2014, and has admitted to the Sars inquiry that Moyane had asked him for a presentation on the tax agency (which he delivered), a year before the suspended commissioner was actually appointed Sars commissioner.

In a submission to the inquiry, the Treasury said that Bain was awarded the contract irregularly and the process was littered with red flags.