A set cost against a task that remains constant regardless of the task duration or the work performed by a resource; for example a delivery of some goods, or some work that has been subcontracted to a third party organization.
'SOURCE; micorsoft project glossary-projectlearning.net
1. Costs that remain constant as production volume varies in the relevant range of production. Fixed cost per unit decreases as total fixed cost is spread over an increasing number of units.2. 'Costs that do not vary with the volume of activity such as accommodation, insurance, depreciation, security and minimum fees for utilities.