Separation happens when you and your partner stop living together as a couple. In this context though, it is possible to be separated but still be living in the same house as your partner. This is commonly referred to as being separated “under the one roof” and your lives would somewhat be similar to being just flat-mates (albeit possibly even less friendly).
While there is no official separation document, there are organisations that you may need to advise of your changed circumstance. For example, you may need to tell Centrelink, if you receive benefits already or if you need financial assistance. You may also need to contact the Child Support Agency; if you have children living with you, you may be entitled to financial payments (child support) from your husband or partner, or you may need to pay child support.
Here are some answers to the most commonly asked questions: