It is an offence under both Commonwealth and State law for a person who is married to go through a form or ceremony of marriage with another person [Marriage Act 1961 (Cth) s 94(1) and Criminal Law Consolidation Act 1935 (SA) s 78]. Under Commonwealth law, the penalty is imprisonment for up to 5 years. Under State law, the penalty is imprisonment for up to 4 years for a first offence and 10 years for a subsequent offence.

It is a defence if the accused can show that they believed on reasonable grounds that their spouse was dead [Marriage Act 1961 (Cth) s 94(2)]. They may be able to show this if their spouse has been continually absent for at least 7 years and they had no reason to believe that their spouse was alive in that period [s 94(3)].

It is also an offence under Commonwealth law for a person to go through a form or ceremony of marriage with a person who is married, if the accused knows, or has reasonable grounds to believe, that the other person is married [s 94(4)]. This also carries a penalty of up to 5 years in prison.

The offence does not apply to a couple who wishes to go through a form or ceremony of marriage with each other more than once [s 94(5)].

The spouse of the accused can be forced to give evidence in a bigamy case, but that evidence alone is not enough to establish that the accused was married at the time of the offence [s 94(6)-(7)].