Judgment of the Court (Eighth Chamber) of 20 May 2021.#FORMAT Urządzenia i Montaże Przemysłowe v Zakład Ubezpieczeń Społecznych I Oddział w Warszawie.#Request for a preliminary ruling from the Sąd Najwyższy.#Reference for a preliminary ruling – Social security – Determination of the legislation applicable – Regulation (EEC) No 1408/71 – Article 13(2)(a) – Article 14(2) – Person normally employed in the territory of two or more Member States – Single employment contract – Employer established in the worker’s Member State of residence – Paid employment activity pursued exclusively in other Member States – Work performed in different Member States during successive periods – Conditions.#Case C-879/19.