SI was founded in 1994 by Paul and Oliver Collyer, but the brothers was developing Championship Manager before they founded SI. In 1992 they started making Championship Manager 1 in their bedroom and they were involved in every CM release until 2003 when SI split with CM publisher Eidos.
In February 2004 they joined in a publishing deal with Sega and they would make start a new Football Management series called Football Manager.
Also in 2004 they announced they would co-develop Markus Heinsohn's Out of the Park Baseball witch went on to become a series consisting of 11 games.
In April 2006 Sega Holdings Europe Ltd acquired SI
In the start of 2007 SI announced they were beginning on an new game. The game would still be a football management game but no more was said.
in April 2007 we found out that the announced game was Football Manager Live. Basically it is Football Manager multiplayer, where up to 1000 people per instance (also known as gameworlds) would play against each other. The game was released in January of 2009. The game uses an database with more than 330.000 football players and 10 playable leagues.
SI are releasing an new and improved version of their award winning Football Manager series every autumn/winter.
Their latest game, Football Manager 2018 came out 9th of November, 2017 and has spent a substantial amount of time at the top of Steam's "top sellers".