A financial centre or financial hub is a location with a significant concentration of participants in banking, asset management, insurance, and financial markets, with venues and supporting services for these activities to take place. Participants can include financial intermediaries, institutional investors, and issuers. Trading activity can take place on venues such as exchanges and involve clearing houses, although many transactions take place over-the-counter (OTC), directly between participants. Financial centres usually host companies that offer a wide range of financial services, for example relating to mergers and acquisitions, public offerings, or corporate actions; or which participate in other areas of finance, such as private equity, hedge funds, and reinsurance. Ancillary financial services include rating agencies, as well as provision of related professional services, particularly legal advice and accounting services.