EU decisions requiring unanimity typically involve areas of significant national interest, such as
common foreign and security policy, taxation, EU finances (long-term budget), and EU citizenship. Unanimity is also required for matters like EU accession (enlargement) and certain aspects of justice and home affairs and social security harmonization.
Key areas requiring unanimity

• Foreign Policy and Security: This includes common foreign and security policy, though certain exceptions may apply for specific, non-military/defense-related decisions.
• Taxation and Finances: Harmonizing national legislation on indirect taxation and deciding on the EU's long-term budget and own resources are subject to unanimous agreement.
• EU Citizenship: Decisions on granting new rights to EU citizens require a unanimous vote.
• EU Membership: The accession of new member states to the EU requires the unanimous consent of all existing members.
• Justice and Home Affairs: Certain provisions, such as those relating to the European Public Prosecutor's Office, family law, or operational police cooperation, need unanimous approval.
• Social Policy: The harmonization of national legislation in the field of social security and social protection requires unanimity.

Other situations requiring unanimity

• Council diverging from Commission proposal:When the Council decides to amend a proposal from the Commission, it must do so unanimously if the Commission does not agree with the amendments.
• Sanctions: While sanctions are a tool of the Common Foreign and Security Policy, decisions on imposing them are taken by unanimity.

https://www.consilium.europa.eu/en/c...tem/unanimity/