The construction industry has for several decades demonstrated a problem with financial crime black labour, while the state loses tens of billions of SEK each year due to tax cuts. The government has been fighting undeclared work for several years, and the construction industry is also working to support healthy competition and remove the unequal working conditions that this entails. The purpose of the study is to examine black labour in small companies in the construction industry, the problems that workers are exposed to and why they choose to work in this way. The study was limited to examining small construction companies and the collection of empirical material took place in the Stockholm region. The work is based on previous findings regarding undeclared work as well as semi-structured anonymous interviews conducted with employers and employees working in two small construction companies in the Stockholm region. Both companies make use of illegal workforce and all respondents who lined up admit that they either work illegally full time or alongside their regular jobs. The results show that the undeclared work does not contain any directly bad or unequal working conditions per se which has been the result in some previous studies. The problem is rather that there is no protection if events occur at work and that the state is withheld tax for work done. Furthermore, the study shows that it is a direct desire of the private individuals who are customers to have the work done as undeclared work.