May I take my customer list when joining a competitor?

Employee who "takes" customer data to competitor = three-layer legal problem. (1) GDPR violation: customer data belongs to employer — employee is not controller, only has "on behalf of employer" access. Taking it = unlawful processing (no basis + purpose-limitation breach). (2) Dutch Trade Secret Act: customer list, price list, marketing strategy = often trade secret. Breach = civil + possibly criminal (Sr Art. 273). (3) Employment contract + non-compete clause: typically ban on transferring "competitively sensitive information". Penalty clauses + non-solicit clauses. What IS allowed? (1) Own network/contacts in your head — not unilateral "data export". (2) General market information + work experience. (3) LinkedIn connections you organically built (grey area — employer-platform-employee-account mix). (4) With employer consent at non-competitor job (healthcare, NGO). Risk: employer can start preliminary injunction for data return + penalty from non-compete + civil damages. Known NL cases have yielded €100k-€500k compensation. Tip: on departure delete all company data from private devices — IT audit possibility exists. On employer accusation: burden of proof on employer to show data was taken + used.