This article examines the institution of customs debt security under the EU Customs Code and the closely related institution of customs debt, without which the former would not exist. The literature review carried out for this article has revealed a serious knowledge gap in this area. Based on the EU Customs Code. Three types of customs securities are presented, provided for in the EU Customs Code: mandatory (obligatory); non-mandatory (optional); not required (exemption), and applied forms of customs securities. The analysis is complemented by a discussion of the debtor’s responsibility for the debt arising by operation of law, focusing on the joint and several liability of customs debtors, which is predominant in economic turnover and constitutes a security mechanism for customs debt coverage. This mechanism on the one hand protects the EU budget and on the other hand, it guards the principle of fair competition on the EU market.