Planning obligations are legal agreements attached to planning application decisions. They are generally called Section 106 agreements (S106) after the section of the 1990 planning legislation formalising them. Planning obligations result from negotiations between the local planning authority and the developer, and are used to secure financial contributions for essential infrastructure such as affordable housing, transport and open space. Planning obligations have become a significant way to deliver affordable homes, despite questions about their ability to deliver sufficient numbers to meet needs in all areas. Further challenges have arisen through recent changes to housing and planning policy. This report examines the role of planning obligations and considers whether more locally effective ways could increase the supply of affordable housing.