In this practice note, Neil Simmonds, a partner in the Financial Services group at Simmons & Simmons LLP and Martin Shah, a partner in the firm's Corporate Tax group, provide an overview of the permissible structures for UK investment funds. This includes discussion of collective investment schemes (CIS), authorised and unauthorised unit trusts, open-ended investment companies (OEICs), investment companies with variable capital (ICVCs), investment trusts, limited partnerships (including private fund limited partnerships (PFLPs)), authorised contractual schemes (ACS), and the various categories of FCA-regulated schemes, namely UCITS schemes, non-UCITS retail schemes (NURS), qualified investor schemes (QIS)), and European long-term investment funds (ELTIFs).