The Executive Committee may draw up and publish Working Rules to clarify the Statutes and Bye- Laws. The General Secretary is responsible to the Executive Committee for not incurring expenditure in excess of the funds designated for that office. The Commissions of the Union shall pursue the scientific objects of the Union by activities such as the study of special branches of astronomy, the encouragement of collective investigations, and the discussion of questions relating to international agreements or to standardization. They remain in office until the end of the ordinary General Assembly next following that of their election. Between two ordinary General Assemblies, Presidents of Commissions may co-opt, from among Members of the Union, new members to the Organizing Committees and to the Commissions themselves.
Commissions draw up their own rules.
Decisions within Commissions are taken according to the vote of their members, and they become effective once they are approved by the Executive Committee. 23 Commissions with related scientific or technical tasks form Divisions. The Divisions coordinate the activities of the affiliated Commissions, including the making of proposals for new Commissions, proposals for dissolving or combining Commissions, and proposals for Working Groups. The Divisions also endorse proposals for IAU Symposia and Colloquia and they may organize Joint Discussions during the General Assemblies. Each Division is directed by a board which is composed of up to six persons including the Presidents of the constituent Commissions.