Founded in 2014 in Hong Kong, BitMEX a peer-to-peer cryptocurrency exchange and derivatives trading website that Hayes co-founded with Ben Delo and Samuel Reed. The exchange is based in the Seychelles.

The platform only handles prices in bitcoin, rather than fiat currencies, meaning that all gains and losses will be in BTC. BitMEX offers a variety of trading services, including margin trading with up to 100 times leverage (meaning that a deposit of $1,000 will result in a trader having the ability to trade $100,000 worth of BTC) and futures trading (allowing investors to bet on the future prices of BTC). In 2016, BitMEX became the first Bitcoin denominated futures contract on a Chinese A Share index.

BitMEX also has a research department that produces reports on the cryptocurrency and blockchain ecosystem.

In 2019, the US Commodity Futures Trading Commission (CFTC) reportedly opened an investigation into BitMEX pertaining to whether the exchange allowed US traders to use its platform. The CFTC has jurisdiction over commodities and derivatives trading in the US, and BitMEX would be required to register with the commission if it wanted to allow Americans to use its platform to trade those products.