The importance of the principle of aggregation of insurance periods for the calculation of the amount of insurance benefits in the light of the latest jurisprudence of the CJEU

The author presents the rules for summing up the periods of insurance, residence or employment, and for the proportional determination of completed insurance periods in the EU Member States. They are absolutely applicable in all situations related to the entitlement to social security benefits by persons moving within the European Union. The application of these principles is illustrated on the example of acquiring the right to an old-age pension. In the latest case C-866/19 SC v. ZUS I Branch in Warsaw, the CJEU ruled that the application of the above principle cannot be limited to the case analyzed in another "Polish" judgment in an earlier, similar case C-440/09. The potential conflict of interpretation applied by the social security courts in the Republic of Poland was resolved by the judgment of the CJEU of 21.10. 2021 in case C-866/19.