It is not compulsory to use the ® and ™ symbols in Australia.
However, as a trademark owner, you should use these symbols when your trade mark is used in social media posts (for example, Facebook posts, LinkedIn posts and even Twitter tweets – where possible). There are a number of reasons for doing this, but notably use of the ® and ™ symbols may discourage potential infringers and may assist in preventing a trade mark from becoming generic.
™ can be used on registered and unregistered trade marks. It gives third parties notice that you consider a particular sign to be a trade mark.
® must only be used next to a registered trade mark. It is an offence to use it in Australia in relation to anything other than a registered Australian trade mark.
If you do not know whether a mark is registered in Australia, you should use the ™ symbol.