Turnkey lump sum in puplic tenders price construction, business increase and decrease

Turnkey construction contracts are a type of contract that started to be implemented in public tenders with the tender legislation that was changed in 2002. The reform efforts carried out in the process of harmonization with the European Union contributed greatly. It is possible to say that the new system, which has been implemented for nearly twenty years, has not settled, and there are probelems in understanding its logic and acting in accordance and glitch with its spirit. While business increases and decreases are not expected to be encountered in turnkey contracts, they occur in almost all contracts as a result of making mistakes. In our study, it is aimed to summarize the lump sum turnkey price, which is a type of construction contracts, in terms of both private law and public law, and it is aimed to investigate in which cases the increase and decrease in work, which is against to the spirit of turnkey, are applied and the mistakes made.