Where insurance undertakings are subsidiary undertakings of an insurance holding company or a mixed financial holding company, group solvency must be calculated under section 250(1), second sentence, and sections 252 to 265, at the level of the insurance holding company or the mixed financial holding company. For this calculation, the insurance holding company or the mixed financial holding company is treated as an insurance undertaking. Its Solvency Capital Requirement must be determined in accordance with Part 2, Chapter 2, Division 2, Subdivisions 2 and 3, and on the assumption that, as regards eligible own funds, it is subject to the provisions laid down in Part 2, Chapter 2, Division 2, Subdivision 1.