The Competition Commission has referred a case to the tribunal for prosecution for alleged price-fixing against 17 banks, including three of South Africa's largest banks.
The watchdog has been investigating a case of collusion and market allocation in the trading of foreign currency pairs involving the rand since April 2015.
The commission said it had discovered that for at least nine years, the banks had agreed to collude on prices for deals for spot trades on trading involving US dollar/rand pairings.
Fin 24, which reported the commission was alleging the banks had broken the Competition Act, named the banks.
"The banks are Bank of America Merrill Lynch International Limited, BNP Paribas, JP Morgan Chase & Co, JP Morgan Chase Bank NA, Investec Ltd, Standard New York Securities Inc, HSBC Bank Plc, Standard Chartered Bank, Credit Suisse Group; Standard Bank of South Africa Ltd, Commerzbank AG; Australia and New Zealand Banking Group Limited, Nomura International Plc, Macquarie Bank Limited, ABSA Bank Limited (ABSA), Barclays Capital Inc, Barclays Bank plc (Respondents)."
The commission also found that the respondents manipulated prices through agreements to refrain from trading and creating fictional bids.
Trading platforms such as Reuters currency trading platform and Bloomberg instant messaging system (chatroom) were mainly used for the deals, the commission added.
This comes after regulations were massively tightened following a previous price-fixing scandal in South Africa, said Bloomberg Markets.
"South Africa's efforts to better regulate foreign-exchange trading follows a price-rigging scandal in which some of the world's largest banks agreed to pay fines and plead guilty to conspiring to manipulate markets after being accused of using online chat rooms to collude. The country's antitrust regulator announced in 2015 that it was investigating banks."