The document which sets out the internal arrangement for the proper management of a company is the

The document that sets out the internal rules for running and managing a company, such as the rights of shareholders, the powers and duties of directors, and procedures for meetings and voting, is the Articles of Association.

The Articles govern the company's internal affairs and how it is administered day to day, which distinguishes them from the other documents listed. The Memorandum of Association instead defines the company's relationship with the outside world, stating its name, objectives, and the scope of activities it is legally permitted to undertake. A prospectus is an invitation to the public to subscribe for shares or debentures, used when raising capital, not a rulebook for internal management. A certificate of incorporation is the legal document issued by the registrar confirming that the company has been formed and now exists as a separate legal entity; it does not contain rules of internal management either.

A helpful way to separate the two founding documents: the Memorandum defines what the company can do and its relationship with outsiders, while the Articles define how the company runs itself internally.