This article explores the different ways in which local governments apply TDR in the absence (uncertainty) of a legal framework and its consequences, focusing on the case of Istanbul in Turkey. Municipalities have implemented mandatory and voluntary TDR through plan notes. For this, the council decisions of Istanbul Metropolitan Municipality are examined, and it is determined which district municipalities use TDR through the plan notes. Semi-structured interviews with a total of 15 actors determined by snowball sampling were used to understand the reasons behind such use. Besides, the use of TDR in Bahçelievler and Arnavutköy districts, one of which is the central district and the other is the periphery district with both widely using TDR, and also examples of districts implementing mandatory or voluntary TDR types by plan notes are examined. The used type of TDR is an alternative for the acquisition of social and technical infrastructure needs in the city, is more open to market influence, and has a voluntary basis. •TDR based on the legal regulation is not commonly used in Turkey.•TDR is implemented in a legally uncertain context through the plan note.•This type of TDR is seen as an alternative tool for the acquisition of urban infrastructure.•This type of TDR is more open to market influence and has a voluntary basis.•Consequences of such use of TDR are difficult to control.