As the most recent comprehensive survey evidence of undeclared work stems from the 2019 Eurobarometer, there is a significant gap in current knowledge about the prevalence and characteristics of undeclared work in Germany. Estimating the true prevalence of undeclared work is complicated, as individuals' responses may be distorted by social desirability bias when asked directly. To address this challenge, this study employs a triangulation of survey-experimental methods, combining a list experiment, a variant of the Randomized Response Technique (the Crosswise model), and direct questioning. Drawing on a quota-based sample of approximately 4,000 individuals balanced by gender, age, and income, the study aims to generate robust prevalence estimates for both the supply and demand sides of undeclared work. Moreover, it investigates the characteristics of undeclared work, such as work hours, hourly wages, and the extent to which labor laws are adhered to, as well as the role of social norms. By systematically comparing results across direct and indirect questioning techniques, the study provides the first large-scale update on undeclared work in Germany in over five years and advances methodological approaches for reducing bias in the study of sensitive economic behaviors more broadly.