The Ownership Links and Enhanced EUTL Dataset provides detailed information on the matching of Person Holding Accounts (PHAs) and Operator Holding Accounts (OHAs) with the companies that own them. We matched the current information on EU ETS account holders to historical information on parent companies, for both groups of these EU ETS accounts. A technical note is provided with a detailed explanation of the matching procedure and the contents of the dataset. In the European Union Emission Trading Scheme (EU ETS), information regarding obligated installations, their respective account holders, compliance and transaction data are stored within the European Transaction Log (EUTL). This data is administered and published at the account level. However, limited and/or incomplete information is provided on the associated firms and sectors. When analysing the data, it is essential to establish links between these EU ETS accounts and parent companies since they are ultimately responsible for the allowance trade these accounts are involved with. In order to increase the scope of research on the EU ETS, several researchers immersed themselves in linking and aggregating EU ETS accounts to obtain EU ETS compliance and transactions data at the company-level. To avoid further duplication of effort by other researchers but also to allow for cross-checking of these EU ETS account linkages, we decided to make the database publicly available. Supported by the European Commission (DG Climate Action), the latest version of this database, The Ownership Links and Enhanced EUTL Dataset , is hosted by the European University Institute (EUI). We gratefully acknowledge permission by Bureau van Dijk to use and publish historical firm ownership data and the associated identification codes.