It may interest you
In the Full Court decision of Kirvan and Tomaras  FamCA 171 the wife sought a decree of nullity in circumstances whereby she had remarried prior to obtaining a divorce certificate from her first husband. Here is a link to the decision for those interested in having a read Kirvan and Tomaras  FamCA 171 – BarNet Jade – BarNet Jade
Whilst this may seem rather trivial on the surface, you should be aware that the Marriage Act sets out that if found guilty of this offence then the maximum sentence is 5 years imprisonment.
Whilst bigamy is not often prosecuted, in Kirvan the Family Court referred the matter prosecution. We are not sure of the outcome of this as the names of the parties in the family law case are anonymized.
You do, however, have a defence to the alleged offence of bigamy if:
1. You believed your wife/husband was dead at the time of your second marriage; and
2. Your wife/husband had been absent in circumstances and for a period of time for you to assume they had died.
If you are still legally married, however your marriage has broken down irretrievably and you have been separated for a continuous period of 12 months or more, if you want to remarry, you should file a Form 3 Application for Divorce for a divorce order to be made so you do not
find yourself in this situation.