There is a legal expectation of foreigners to declare their money when they enter South Africa, the SA Revenue Service (Sars) said on Thursday.
"For foreign nationals there is no limitation [on the amount they can bring in], but there is a legal expectation to declare it at customs," Sars spokesman Adrian Lackay said.
"You are then issued with a form in case you encounter any difficulties when you in the country... This is a legal obligation on the traveller."
Lackay was issuing a warning after R1.9 million was reportedly stolen from an investment banker linked to the Arab royal family. It was apparently taken from the safe in his Sandton hotel room.
According to a report on Wednesday, Farid Alshabbar said he went out for dinner on Saturday night, and when he returned to his hotel room an hour later to fetch more money it was gone.
"My money was gone. They were so stupid they left the 1kg gold pellets (worth US46,000 or about R372,160) inside the safe," Alshabbar was quoted as saying.
He suspected that hotel staff were responsible. A porter has since been arrested and police were still looking for the hotel's head of security.
Lackay said Sars had since met with Alshabbar and his lawyer.
"What is of concern is when South Africa has a well-regulated banking system... there should be little need for someone to carry large amounts of money on their person."
When people carried large amounts of money it could arouse suspicion, he said.