The Special Investigating Unit is an independent statutory body that was established in terms of the Special Investigating Units and Special Tribunals Act, Act No. 74 of 1996 (SIU Act).

The primary mandate of the SIU is to investigate serious allegations of corruption, malpractice and maladministration in the administration of State institutions, State assets and public money as well as any conduct which may seriously harm the interests of the public, and to recover any financial losses suffered by State institutions through civil ligation. The SIU is empowered to take civil action to correct any wrongdoing it uncovers in its investigations.

The SIU investigations are dictated by the issuing of a Presidential Proclamation, and then to institute civil litigation proceedings either in a Special Tribunal or a High Court for the prevention or recovery of financial losses suffered by the State. Once the investigation is completed, a final report is submitted to the President with an overview of the investigation and its findings, as well as the various recommendations made and their outcomes.

The SIU receives allegations either through its whistle-blower hotline, which is managed by an independent service provider; directly from state institutions themselves; or alternatively through direct approaches from whistle-blowers, be it through walk-ins, telephone calls or emails.

The SIU has powers to subpoena witnesses, bank statements and cellphone records, search, seize evidence and interrogate witnesses under oath and to litigate on behalf of the State. In line with SIU Act, the SIU refers evidence pointing to criminal conduct uncovered during its investigations to the attention of the National Prosecuting Authority (NPA) for prosecution.