If you get married under customary law, the marriage is considered valid and legal in terms of the Recognition of Customary Marriages Act (RCMA). If the marriage isn't registered with the Department of Home Affairs, it is still legal and valid. But if the husband marries a second wife and that marriage is registered at the Department of Home Affairs but the first marriage isn't registered, the first marriage will be invalidated. #StaySmart register your customary marriage to ensure that you are protected.
(Please note: This is only general advice and should not be relied on solely. The law is complicated and there are many influencing factors that can change the above).