One of the most important and basic principles of organisation is division of work. No one person can discharge everything well and as such what a person can perform best is devised which is called division of work or specialisation. At the top management level the work is divided on the basis of functions. At the middle level the work division is done on the basis of product or customers and on the lower level the work division is made on the basis of serial plan or parallel plan. In serial plan the work is divided into series of small jobs and work passes through all these stages for completion. Each stage of operation is entrusted to an employee who is a specialist in his line. After completion of his work he passes it to other. The following diagram is a serial plan of work division in respect of internal mails.
In parallel plan of work division, the work is divided into various parts and each part is assigned to a team of individuals. Each individual performs all the operations of that process. The process of concurrent handling of operation by an individual is called parallel plan of arrangement. The employees are not specialist in one part of the operation but gain proficiency in doing several operations.