A Turnkey, a turnkey project, or a turnkey operation ( also spelled turn-key ) is a type of project that is constructed so that it can be sold to any buyer as a completed product. This is contrasted with build to order, where the constructor builds an item to the buyer's exact specifications, or when an incomplete product is sold with the assumption that the buyer would complete it.
A contract where the essential design emanates from, or is supplied by, the Contractor and not the owner, so that the legal responsibility for the design, suitability and performance of the work after completion will be made to rest… with the contractor. 'Turnkey' is treated as merely signifying the design responsibility as the contractor's.
A turnkey computer system is a complete computer including hardware, operating system and application(s) designed and sold to satisfy specific business requirements.