S1 Corporation
| Company type | Private (before acquisition) |
|---|---|
| Industry | Software development, Financial services software |
| Defunct | 2012 |
| Fate | Acquired by ACI Worldwide, Inc. |
Area served | Banks, retailers, credit unions |
Key people | James (Chip) S. Mahan III (CEO 1994–2001, 2005), Jaime Ellertson (CEO until 2005), Johann Dreyer (CEO 2006–2012) |
| Products | Software solutions for payment processing and financial services for ATMs and retail point of sale platforms |
| Parent | ACI Worldwide, Inc. |
S1 Corporation was a U.S.-based software development firm located in Norcross, Georgia, focusing on software solutions for payment processing and financial services tailored to automated teller machines and retail point of sale platforms. Its primary clientele consisted of banks, retailers, and credit unions. In October 2011, S1 was purchased by rival company ACI Worldwide, Inc. at a price of $9.95 per share, resulting in a transaction valued near $515.7 million.
Initially established as the technology branch of Security First Network Bank, S1 grew through strategic acquisitions such as the South African company Mosaic Software in 2004 and the internet banking provider PM Systems Corporation in 2010. In 2011, S1 attempted to acquire Israeli banking services provider Fundtech Ltd; however, it was outbid by the private equity group GTCR. Soon after, ACI Worldwide successfully completed its takeover of S1 following several bidding rounds.
The company's leadership history includes James (Chip) S. Mahan III serving as CEO from 1994 to 2001, followed by Jaime Ellertson until 2005, when Mahan resumed the role. Johann Dreyer, formerly CEO of Mosaic Software, assumed the position of S1’s final CEO in 2006 and remained until the firm's acquisition by ACI Worldwide in 2012.