The aim of this report is to provide a systematic overview of the extent and nature of undeclared work, and how it is being tackled, in the EU candidate country of Turkey. The objectives of the report are to analyse the prevalence and character of undeclared work in Turkey; to examine how the fight against undeclared work is organised; and to review relevant policy approaches and measures adopted. Throughout the report, the situation in Turkey is compared with the EU27 wherever feasible. This report forms part of a research study into undeclared work in five countries: four candidate countries for EU membership (Iceland, Montenegro, Turkey and the former Yugoslav Republic of Macedonia) and one acceding country, Croatia.