City Index was founded by Chris Hales and Jonathan Sparke in September 1983, initially backed by a $4 million investment from a US shareholder. The company began operations in March 1984, pioneering
spread betting for retail clients. In 2001, City Index introduced
contracts for difference (CFD). In 2005, it acquired
IFX Group, owner of FX broker
IFX Markets and spread betting provider
Finspreads, a London-based company founded in 1999. The Finspreads brand was relaunched in January 2013 but ceased operations on 24 March 2018, when all existing Finspreads accounts were migrated into City Index. In 2006, the company opened offices in
Sydney,
Singapore, and
Shanghai to serve clients across the
Asia Pacific region. In 2008, City Index acquired US-based
FX Solutions, the New Jersey-based FX broker. In October 2009, it launched the City Trading app, the first spread betting and CFD mobile platform for the
iPhone, later expanding to
Android and
BlackBerry. During the
2008 financial crisis, Spencer provided a £70 million capital injection to stabilize the company after significant trading losses. Despite this, in March 2009 City Index briefly breached its banking covenants. The merged company had roughly 235,000 clients in 180 countries with annual trading volumes exceeding $3 trillion. GAIN Capital had attracted acquisition interest from several bidders since mid-2019. In June 2020,
INTL FCStone (later renamed StoneX Group) made an acquisition offer at $6 per share, valuing the deal at approximately $236 million. Due to GAIN Capital's strong recent performance, including Q2 2020 net revenue of $101 million, many shareholders considered the offer undervalued, and some supported an alternative proposal by JB Capital at $6.25 per share. Despite this shareholder opposition, the deal with INTL FCStone was eventually finalized. The acquisition was also marked by an
insider trading scandal involving Joseph Conlan, a former financial services executive at GAIN Capital. Conlan learned confidential details about the pending acquisition from a friend employed at StoneX and purchased GAIN Capital shares ahead of the public announcement. The case concluded with Conlan agreeing to a cease-and-desist order and paying $159,389 to settle regulatory charges. Following the acquisition by StoneX Group, City Index became part of StoneX's global retail brokerage division. Under the new ownership, City Index UK's legal entity was renamed StoneX Financial Ltd, though the City Index brand continued to operate specifically for retail customers. In 2022, City Index underwent a rebranding and updated its trading platforms to include Advantage Web Trader,
TradingView, and
MetaTrader 4. In April 2025, City Index Singapore transitioned to
Forex.com, another StoneX subsidiary. On 30 August 2025, City Index's Australian operations were rebranded to Forex.com as StoneX moved to consolidate its retail trading businesses under a single global brand. At the same time, StoneX made changes to its regulatory structure: Gain Capital UK (City Index’s former parent company) obtained a Category 5 license from the UAE's
Capital Market Authority (CMA) in August 2025, with plans to transfer it to StoneX Financial Ltd and eventually surrender Gain's UK FCA licence. StoneX Financial Ltd (formerly City Index's UK entity) remains the primary FCA-authorised entity for City Index and FOREX.com in the UK. == Marketing and sponsorship ==