This study presents survey evidence on the magnitude and determinants of tax compliance costs in Flemish small and medium-sized enterprises (SMEs). Data were obtained from an Internet questionnaire among members of a professional network of Flemish entrepreneurs, called VOKA. Analyzing a sample of 151 Flemish SMEs, we find that the tax compliance costs—exceeding over 7% of gross added value—are relatively high. Value-added tax, labor taxes, and corporate taxes are the main components of tax compliance costs. In addition, our evidence confirms the regressivity hypothesis, according to which smaller companies face relatively higher compliance costs. Furthermore, industry, age, and the proportion of blue-collar workers prove to be determining factors of relative compliance costs. Our study concludes by formulating a number of policy recommendations that might contribute to lower compliance costs.