Important:
This answer is based on tax law for the year ending 28 February 2020.
Answer:
This is not a matter that a controlling body for tax practitioners can assist with. You must take the matter up with SARS.
According to the SARS website, one can report suspicious activities by:
Completing out a Suspicious Activity Report online at www.sars.gov.za or
Calling the SARS Fraud and Anti-corruption Hotline on 0800 00 2870.
You can also report it to the national prosecuting authority.