In Australian politics, branch stacking is the act of enrolling persons to a party by offering inducement, or enrolling persons for the principal purpose of influencing the outcome of internal preselections.

Branch stacking activities can include:

• The payment of the party's membership fee as an inducement for that person to join the party
• To pay the membership fee of a person who is unwilling to pay their own membership
• To pay for membership for any person unaware that membership has been taken on their behalf.
• To pay membership for a person on the precondition that the member is then obliged to vote in a particular way.
• The encouragement of a person to join for the express purpose of influencing the outcome of a ballot within the party.
• The enrol, encourage or assist a member to enrol on the electoral roll at an address that is not their principal address.
• To organise or pay for concessional rate fees for a person who is ineligible for that rate without reasonable belief that they were entitled to that rate.
• To recruit members who do not live at the claimed address of enrolment.

In 2004-2005, a major scandal developed over branch stacking within the Victorian Branch of the Australian Labor Party, largely over the failure of members of Labor Unity on the Party's Administrative Committee to follow the party rules to investigate allegations of branch stacking the seats of Gorton, Gellibrand, Corio and Isaacs. [1]