You and your partner do not need to agree for separation to happen, but at least one of you needs to make a decision to separate, act on that decision and tell the other person.

You might need to be able to show that you have separated and when you separated. The date of separation may also be relevant in property settlement proceedings. You do not need to sign anything but it is a good idea to keep a clear record of what property you have at the time of separation, what you took with you, and what you left behind.

It is always a good idea to get legal advice when you separate from a marriage or defacto relationship, particularly if it has been a long-term relationship.  You can do so before you split, or just after you separate so that you can be aware of any time limits or other things that might affect you.

Keep in mind that you may also need to report your separation to Centrelink.