After presenting the principle of joint liability as an exception within civil law (article 1041 Civil Code) or as a rule in commercial law (article 42 Commercial Code), this study analyzes the joint liability in fiscal law. Thus, according to article 27 of the Code of Fiscal Procedure, they are jointly liable with the insolvable debtor: the natural person which had caused, intentionally, the insolvability (the contracting party, the shareholder, the administrator) or the legal person which, exercising a direct or indirect control, performs a similar or identical activity as the insolvable debtor, uses the tangible assets of the debtor (at least 50% of the accounting value), has contractual commercial relations with the clients or the suppliers (at least 50% of the clients or the suppliers are common to the person and the debtor) or has civil or labor relations with at least 50% of the debtor’s employees.