Separation of duties (SoD), also known as segregation of duties, is the concept of having more than one person required to complete a task. It is an administrative control used by organisations to prevent fraud, sabotage, theft, misuse of information, and other security compromises. In the political realm, it is known as the separation of powers, as can be seen in democracies where the government is separated into three independent branches: a legislature, an executive, and a judiciary.

Separation of duties is a key concept of internal controls. Increased protection from fraud and errors must be balanced with the increased cost/effort required.

In essence, SoD implements an appropriate level of checks and balances upon the activities of individuals. R. A. Botha and J. H. P. Eloff in the IBM Systems Journal describe SoD as follows.

Separation of duty, as a security principle, has as its primary objective the prevention of fraud and errors. This objective is achieved by disseminating the tasks and associated privileges for a specific business process among multiple users. This principle is demonstrated in the traditional example of separation of duty found in the requirement of two signatures on a cheque.

Actual job titles and organizational structure may vary greatly from one organization to another, depending on the size and nature of the business. Accordingly, rank or hierarchy are less important than the skillset and capabilities of the individuals involved. With the concept of SoD, business critical duties can be categorized into four types of functions: authorization, custody, record keeping, and reconciliation. In a perfect system, no one person should handle more than one type of function.

Principally several approaches are optionally viable as partially or entirely different paradigms:

A person with multiple functional roles has the opportunity to abuse those powers. The pattern to minimize risk is:

General categories of functions to be separated: