This study examines factors associated with openness to un­declared and under-declared work among dependent em­ployees in the European Union, focusing on individuals who have not reported recent engagement in informal employ­ment. Using Special Eurobarometer 92.1 microdata and logistic regression models, it adopts a preventive perspec­tive on potential vulnerability to informality. The analysis shows that openness is associated with socio-demographic characteristics, including age, gender, household composi­tion and social class, as well as employment context, prior exposure to informal practices, tax morale, perceived detec­tion risk and expected sanctions. The results also indicate that fully undeclared and under-declared work should not be treated as interchangeable, as they are associated with partly distinct individual, household and enforcement-re­lated patterns. In addition, item nonresponse suggests possible concealed familiarity with informality, although robustness checks indicate that alternative codings do not materially change the results. While pension outcomes are not directly estimated, the findings are relevant to debates on social protection, as openness to informal employment may indicate vulnerability to future contribution gaps if it translates into actual undeclared or under-declared work. By highlighting factors associated with early-stage openness to informality, the study contributes to discussions on la­bour market formalisation and preventive policy interven­tions aimed at supporting formal employment and long-term income security.