51Under the first paragraph of Article 266 TFEU, the institution whose act has been declared void must take the necessary measures to comply with that judgment with ex tunc effect. That entails, inter alia, the payment of sums unduly collected on the basis of that act and the payment of interest (see, to that effect, judgments of 12 February 2015, Commission v IPK International, C‑336/13 P, EU:C:2015:83, paragraph 29, and of 5 September 2019, European Union v Guardian Europe and Guardian Europe v European Union, C‑447/17 P and C‑479/17 P, EU:C:2019:672, paragraph 55).
15 judgesK. Lenaerts, L. Bay Larsen, A. Arabadjiev, C. Lycourgos, E. Regan, F. Biltgen, N. Piçarra, Z. Csehi, P.G. Xuereb, L.S. Rossi, N. Jääskinen, N. Wahl, I. Ziemele, J. Passer, D. Gratsias