Adults can use a surname they want without having to register it. A surname is acquired in common law by usage. This means that you can choose any last name and use it without having to register it. Take for example Kim Schmitz, who is more commonly known as Kim Dotcom.

Changing your surname after marriage or civil union

In the context of marriage, this means that you don’t have to go through any special processes if you want to change your surname after you get married or have a civil union. You can simply start using the last name on all your documentation.Your driver’s license and passport are the two big legal documents with your previous surname. You can either wait for these to expire and update them with your new surname. Otherwise, you can pay for them to be reissued. When it comes to proving your surname, different organisations generally have differing rules for proving ID, but you can use your marriage certificate as proof to show you have taken your partner’s last name. The same rules apply if you decide you want to go back to using your previous surname post-separation.

Changing your child’s surname

For children under 18, a common reason to change their surname is so they could share their parent’s new surname after marriage. When a child’s surname is changed all parents or legal guardians of the child must sign an official form before the child's name can be changed.Alternatively, if the parents or legal guardians cannot agree on whether to change the surname of the child or what to change it to, it becomes a guardianship issue. If the guardianship issue is not resolved, it can end up in the family court with a full hearing. Often judges are reluctant to change the surname of a child unless there is a good reason to do so. The chosen name must meet the guidelines set out by section 18(1) of the Births, Deaths and Marriages, and Relationships Registration Act 1995. The general rule is that the registrar will not permit names that are against public policy. Examples of some names that have been declined by the Department of Internal Affairs in 2017 include grammatical symbols such as ‘/’ and ‘.’ and names that implied the child held a rank or title such as ‘Justice’, ‘Prince’, ‘Duke’ and ‘Royal’. The Department of Internal Affair’s also banned names of religious origin including ‘Christ’ and ‘Messiah’.