| Southern & Western Support Ltd | Health & social care | 2020 |
| Southern Acoustics UK Ltd | Information & communication | 2020 |
| Southern and Western Properties Ltd | Real estate | 2022 |
| Southern Cleaning Services (Sussex) Limited | Administrative & support | 2002 |
| Southern Counties Scaffolding Ltd | Construction | 2020 |
| Southern Couriers Ltd | Transport & logistics | 2010 |
| Southern Creations Ltd | Hospitality | 2006 |
| Southern Crew Ltd | Other services | 2004 |
| Southern England Estates Development Co Limited | Real estate | 1946 |
| Southern England Wines (UK) Ltd | Agriculture & fishing | 2016 |
| Southern Hospice Group | Health & social care | 1968 |
| Southern Hospice Trading Limited | Wholesale & retail | 2010 |
| Southern ID Ltd | Administrative & support | 2022 |
| Southern Investment Network Ltd | Financial services | 2013 |
| Southern PC Doctor Limited | Other services | 2019 |
| Southern Piling Limited | Construction | 2000 |
| Southern Property Group Ltd | Real estate | 2019 |
| Southern Property Rental Ltd | Real estate | 2023 |
| Southern Seas (European Agencies) Limited | Professional & scientific | 2013 |
| Southern Sparks Electrical Ltd | Construction | 2013 |
| Southern Surveyors and Property Consultants Ltd | Professional & scientific | 2015 |
| Southern Surveyors Limited | Professional & scientific | 2017 |
| Southern Waste Solution Ltd | Water & waste | 2025 |
| Southern Water (Greensands) Financing PLC | Administrative & support | 2011 |
| Southern Water (NR) Holdings Limited | Professional & scientific | 2003 |
| Southern Water Capital Limited | Administrative & support | 2002 |
| Southern Water Executive Pension Scheme Trustees Limited | Administrative & support | 1990 |
| Southern Water Industries Limited | Professional & scientific | 1988 |
| Southern Water Investments Limited | Professional & scientific | 2003 |
| Southern Water Limited | Professional & scientific | 1989 |
| Southern Water Pension Trustees Limited | Administrative & support | 1990 |
| Southern Water Retail Services Limited | Water & waste | 2014 |
| Southern Water Services Group Limited | Professional & scientific | 2002 |
| Southern Water Services Limited | Water & waste | 1989 |
| Southfields Clinic Limited | Health & social care | 2009 |
| Southstar Computers Limited | Information & communication | 1996 |
| Sovereign 2017 LLP | | 2017 |
| Sovereign Alarms Limited | Administrative & support | 1989 |
| Sovereign Hub Ltd | Wholesale & retail | 2025 |
| Sovereign Motors (Worthing) Limited | Wholesale & retail | 2018 |
| Sovereign Motors Ltd. | Wholesale & retail | 1998 |
| SOW Consulting Limited | Professional & scientific | 2025 |
| Soxo Property Ltd | Real estate | 2026 |
| Sozo Soma Limited | Health & social care | 2020 |
| Sp:In LDN Ltd | Professional & scientific | 2021 |
| Spa Pro Ltd | Wholesale & retail | 2017 |
| Space Mode Limited | Professional & scientific | 2015 |
| Space Station Soft Play Ltd | Hospitality | 2025 |
| SPACE16 Limited | Information & communication | 2021 |
| Spacekonzept Limited | Real estate | 2018 |
| Spanjar & Sons Limited | Manufacturing | 2012 |
| Sparkle Multi-Academy Trust | Education | 2015 |
| Sparkling Clean (South) Ltd | Administrative & support | 2025 |
| Spartacus Educational Publishers Limited | Professional & scientific | 1987 |
| Spatham Farm Consultancy Ltd | Administrative & support | 2023 |
| Spchd Limited | Professional & scientific | 2016 |
| Speakit Films Ltd | Information & communication | 2015 |
| Speakit Productions Ltd | Information & communication | 2004 |
| Speakit Studios Ltd | Information & communication | 2020 |
| Special Publishing Ltd | Administrative & support | 1996 |
| Specialist Prescribing Group Ltd | Health & social care | 2024 |
| Speciality Breads Limited | Manufacturing | 1996 |
| Speciality Food Manufacturing Limited | Manufacturing | 2011 |
| Spectre Tech Limited | Manufacturing | 2017 |
| Spectrum Professional Development Limited | Professional & scientific | 2014 |
| Spectrum Surveyors Limited | Administrative & support | 2003 |
| Specular Systems Limited | Information & communication | 2010 |
| Speed 6310 Limited | Real estate | 1997 |
| Speed-Sure Logistics Limited | Transport & logistics | 2006 |
| Speedcut Engineering Limited | Professional & scientific | 2025 |
| Spellbound Aerial Ltd | Administrative & support | 2024 |
| Spencer Builders Limited | Construction | 2014 |
| Spences Four LLP | | 2015 |
| Spences One LLP | | 2011 |
| Spences Three LLP | | 2013 |
| SPF Services Ltd | Professional & scientific | 2023 |
| Spgrp Ltd | Wholesale & retail | 2011 |
| Sphourti Digital Limited | Professional & scientific | 2022 |
| Spice Village (Rustington) Limited | Hospitality | 2017 |
| Spiderama Limited | Professional & scientific | 2015 |
| Spiral Services Limited | Professional & scientific | 2017 |
| Spire Developments Limited | Construction | 2002 |
| Spireswood Building Services Ltd | Construction | 2020 |
| Spiritus Games Ltd | Information & communication | 2016 |
| Spitfire Creative Ltd | Administrative & support | 2014 |
| Spitfire Property Limited | Construction | 2026 |
| SPK Search Ltd | Administrative & support | 2015 |
| Splashpoint House Ltd | Information & communication | 2024 |
| Split Stone Games Ltd | Manufacturing | 2023 |
| Sports Connections Limited | Arts & recreation | 2006 |
| Spottiswoode Properties Limited | Real estate | 2024 |
| Spring (UK) Ltd | Other services | 2014 |
| Spring Marketing Communications Limited | Professional & scientific | 2002 |
| Springbok UK Properties Ltd | Real estate | 2019 |
| Springfield Secretarial Services Limited | Administrative & support | 1997 |
| Springs Gym Limited | Arts & recreation | 2021 |
| Spudsrus Ltd | Hospitality | 2025 |
| SPZ Associates Ltd | Professional & scientific | 2012 |
| SQL Training Ltd | Information & communication | 2017 |
| Squared M Properties Ltd | Administrative & support | 2020 |