The composition of Seanad Éireann is defined in outline by Article 18 of the Constitution of Ireland, which provides for 11 appointees of the Taoiseach, 6 senators elected by the universities, and 43 senators elected by 5 vocational panels.
The composition of each panel and procedures for the election are laid down by the Seanad Electoral (Panel Members) Act, 1947.
Section 52 of the 1947 Act defines the numbers of senators to be elected from each of the panels. The Act also provides for the division of each panel into two sub-panels: the nominating bodies sub-panel and the Oireachtas sub-panel; and for the election of Members from the panels and sub-panels as follows:
|Panel||Senators||Min. no. from|
|Cultural and Educational Panel||5||2|
|Industrial and Commercial Panel||9||3|
Candidates must be Irish citizens over the age of 21. Candidates can be nominated by two methods: by Oireachtas members or by nominating bodies. Nominating bodies are organisations that are connected to the particular vocation, for example, the Irish Congress of Trade Unions can nominate in the Labour panel, and the Royal Irish Academy can nominate in the Cultural and Education panel.
As the electorate is restricted to elected councillors, TDs and senators, the political parties have a great influence in the nomination procedures. The main political parties are aware of how many seats they will win after the Dáil election and will endorse candidates that they deem to have a chance of election to the Dáil in the next general election. The nominating bodies tend to nominate party members. Even where non-party candidates get on the ballot paper, it is very rare that these candidates are successful.
The electoral college for the vocational panels are city and county councillors, members of the new Dáil and members of the outgoing Seanad. The electorate consists of approximately 1,000 voters.
Voting is conducted by proportional representation by the single transferable vote. However, each ballot is given the value of 1,000 to aid the transfer of fractions of votes.
There is a guaranteed minimum number of members that can be elected from each sub-panel. This was designed to allow nominating bodies a greater influence in the election of Senators. However, in practice, the political parties also dominate the nominating bodies sub-panel nominations and the electorate.
In a by-election to the vocational panels, the nomination procedure is the same. However, as there is only one seat available, there can be no minimum number elected from sub-panels. The electorate for a by-election for a vocational panel seat are members of the Dáil and Seanad so the Government party or parties win the seat unless there is a cross-party arrangement.