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SUMMARY: 1. Introduction. – 2. Financial solidarity in EU budget: preliminary remarks. – 2.1. Solidarity within the EU revenue system. – 2.2. Solidarity within the EU expenditure. – 3. Next Generation EU: a new paradigm of financial solidarity? – 3.1. NGEU: innovations on the revenue side. – 3.2. NGEU: innovations on the spending side. – 4. Concluding remarks: solidarity as a driven force for the interpretation and development of EU budgetary law.