When a casual vacancy occurs in the Seanad through the death, disqualification or resignation of a sub-panel member, the vacancy is filled by a by-election.
To be nominated as a candidate for an Oireachtas sub-panel vacancy, any 9 members of the Dáil or Seanad must jointly nominate you. To be nominated as a candidate for a Nominating Bodies sub-panel vacancy, you must be nominated by a registered nominating body for the relevant panel.
The electorate at a by-election is composed of members of the Dáil and the Seanad only. Voting is by secret ballot. The counting procedure is the same as at the general election except that only one candidate will be elected.