Abstract This chapter argues that the work of the European banking union remains incomplete in one important respect: the structural re-organization of large European financial firms that would make resolution of a systemically important financial firm a credible alternative to bail-out or some other sort of taxpayer assistance. It argues that were EU financial firms to move to a holding company structure, the focus of resolution can be at the holding company (‘HoldCo’) level, minimizing disruption of the ordinary business of the operating financial subsidiaries. A vital addition to structural renovation is the requirement of a holding company form for systemically important financial institutions in the EU. The chapter suggests that it might be possible to achieve such an outcome via a number of different channels, which it goes on to review and concludes that the mandatory structure should become a public HoldCo parent for the operating subsidiaries of the banking group, set up so that the assets of HoldCo consist of shares in its subsidiaries, and that its liabilities are confined to unsecured term debt. This was the missing piece of the proposed Structural Measures Regulation and remains a missing piece for a credible Single Resolution Mechanism in the banking union.