The parties must have the appropriate capacity to enter into a valid marriage. For marriages under the Marriage Act 1961, minors between the age of puberty and the age of majority must have the consent of both parents or a guardian. If the minor has only one parent living, only that parent's consent is required. Where the minor has a guardian, the guardian's consent is needed. If the minor has no parent or guardian, permission must be obtained from the Commissioner of Child Welfare. Additional consent is required from the Minister of Home Affairs if the male minor is under the age of 18 and the female is under the age of 15. For marriages and civil partnerships under the Civil Union Act, the age of consent is 18. 

In terms of common law, insane persons cannot enter into a valid marriage. This is due to their lack of understanding of the nature of the juristic act and the obligations that marriage creates. Where a person marries whilst they are already validly married to someone else, the second marriage will be bigamous and therefore void. Bigamy is a criminal offence.  Both parties must have the intention to conclude a marriage as understood by the law. 

This is evidenced by their declarations to the marriage officer during the marriage ceremony. Consensus will be excluded by a material mistake as to the spouse's identity or the nature of the juristic act, duress or undue influence, or prenuptial stuprum.  The law also prohibits marriage between certain blood relations (relationship of consanguinity) and certain persons related through marriage (relationship of affinity). Marriages within these prohibited degrees of relationship are not valid and are in fact, void.  

The formal requirements for entering a valid marriage are contained in the Marriage Act (25 of 1961) and the Civil Union Act (17 of 2006). A duly appointed marriage officer must solemnise the marriage, each party must produce an identity document or an affidavit in the prescribed form, and a minor must produce written consent of their parent(s) or guardian. The marriage officer must solemnise the marriage according to the prescribed formula in the presence of the two parties to the marriage and in the presence of two witnesses. All marriages must be registered. If the prescribed formalities are not complied with, the marriage is void marriage.