Focusing upon any country, this PhD will focus upon the practice whereby a formal employer will pay a formal employees not only an official declared salary but also an additional undeclared (envelope) wage. This usually involves a verbal employment contract being agreed which replaces the official written contract of employment. The intention of this PhD is to explore what this verbal contract involves such as whether it involves an agreement to work longer hours, not take official holiday entitlements, undertake tasks and jobs not in the official contract, etc. Until now, this has never been analysed. Given that up to 30% of jobs in some Eastern and Central European countries involve envelope wages, it is an important issue to understand.