The transfer of rights and/or obligations by one person to another particularly with reference to a contract, so that under certain strictly defined conditions the second person takes over those rights and obligations and can enforce them, or have them enforced against him. For certain typesof assignment the permission of a third party must be obtained. A building contractor can assign work to a subcontractor without the permission of his employer but an artist employed to paint a portrait cannot assign the work to another artist without permission. Generally speaking, a person cannot assign a duty to another when it is of a personal nature. The owner of a business who sells cannot assign to the purchaser the various contracts of employment which he has made. Assignment falls into three categories. Where there is an agreement that A shall do something for B, A may wish to assign his obligation to C; similarly B may wish to assign the benefit to D: (1) Basically A may assign with the permission of B. This then becomes in effect new agreement between B and C, and A is no longer concerned. (2) A may assign to C by custom of trade, e.g. subcontracting. B cannot complain but has a remedy both against A and against C. (3) A may assign without consulting B and without having any implied right by trade to do so. B may ignore the assignment and treat A as wholly responsible and as having breached the original agreement. Where B is assigning the benefit much the same rules apply.
Reference: The Penguin Business Dictionary, 3rd edt.