Line of business restrictions (LOBRs) are antitrust remedies or regulatory restrictions that can be used to limit the range of activities that a firm can undertake. They include separation restrictions ranging from structural separation to weaker forms of behavioural separation (accounting, functional and legal separation). However, there are also alternative behavioural restrictions including mandating access, non-discrimination obligations and mandatory standards on portability and interoperability. This paper discusses each of these types of restrictions. It was prepared as a background note for a discussion held at the OECD in June 2020 on Lines of Business Restrictions.