Oath or affirmation of office
The Constitution, section 42, requires senators to make and subscribe (sign) before the Governor-General, or some person authorised by the Governor-General, an oath or affirmation of allegiance in the form set out in the Constitution.
Senators make and sign the oath or affirmation at the first sitting of the Senate which they attend after the commencement of their terms as senators. Senators taking their places after a periodical or general election are sworn in by the Governor-General. Senators taking their places at other times are usually sworn in by the President, who is authorised by the Governor-General, in accordance with section 42, to administer the oath or affirmation.
Section 42 requires that a senator make and subscribe the oath or affirmation before taking the senator’s seat in the Senate. A senator must therefore be sworn in before sitting in the Senate or participating in its proceedings, but there is nothing to prevent a senator performing other official functions before taking the oath or affirmation. Thus the Senate appoints senators to committees, and senators may participate in the proceedings of those committees, before they have been sworn in. For this purpose, membership of committees is often changed with effect from the date of commencement of the terms of new senators who are appointed to committees.