| Savannah Spa Therapy Ltd | Other services | 2024 |
| Savick Limited | Information & communication | 2015 |
| Saxby Construction Ltd | Construction | 2015 |
| Saxon Lodge Properties Limited | Real estate | 2025 |
| SAY Southern Plumbing & Heating Limited | Construction | 2023 |
| SB Services Southampton Limited | Administrative & support | 2018 |
| Sbkd Properties Ltd | Real estate | 2024 |
| SC Maintenance Group Ltd | Construction | 2026 |
| Scareaway Systems Limited | Wholesale & retail | 2016 |
| SCF Consultancy Limited | Professional & scientific | 2008 |
| SCG Electrical (UK) Ltd | Construction | 2012 |
| School Farm Equestrian Limited | Other services | 1995 |
| School Farm Estates Limited | Real estate | 1985 |
| School Lane Holdings Limited | Real estate | 1992 |
| Schreuder Health Limited | Health & social care | 2012 |
| Schusterbruce Limited | Health & social care | 2010 |
| Scratched Cars Limited | Wholesale & retail | 2014 |
| SD RAD Medics Limited | Health & social care | 2014 |
| SDG Carpentry & Shopfitting Limited | Construction | 2012 |
| SDM Fuel Solutions Limited | Manufacturing | 2011 |
| SDM Maintenance Services Limited | Construction | 2024 |
| Sea POP Ltd | Professional & scientific | 2015 |
| Seans Floors Ltd | Construction | 2023 |
| Seascape Consultants Ltd | Professional & scientific | 2010 |
| Secad Technical Limited | Construction | 2005 |
| SEED2SMOKE Consulting Limited | Professional & scientific | 2018 |
| Sell MAX Ltd | Wholesale & retail | 2022 |
| Selzer-Blackiston One Ltd | Extraterritorial | 2023 |
| SEM HR Consulting Limited | Administrative & support | 2009 |
| Semco Services Limited | Construction | 2000 |
| Semco Steel Fabricators Limited | Manufacturing | 2026 |
| Semur Limited | Health & social care | 2025 |
| Senator Security South Limited | Administrative & support | 2007 |
| Sengco Limited | Agriculture & fishing | 2014 |
| Senior Orthopaedics Limited | Health & social care | 2011 |
| Sennitt Planning Limited | Construction | 2017 |
| Sepraflux Consultancy Ltd | Professional & scientific | 2025 |
| Servihome Ltd | Construction | 2026 |
| SES Autoparts (Holdings) Limited | Financial services | 2020 |
| SES Autoparts Group Limited | Financial services | 2024 |
| SES Autoparts Limited | Wholesale & retail | 1994 |
| Setting OUT Solutions (Southern) Ltd | Construction | 2007 |
| Seven Seas Commercial Services (UK) Limited | Wholesale & retail | 2002 |
| SEW Equestrian Limited | Wholesale & retail | 2016 |
| SG Properties (London) Ltd | Construction | 2012 |
| Shaftbox Limited | Information & communication | 2020 |
| Shamblers Yard Ltd | Administrative & support | 2017 |
| Shampooo Ltd | Other services | 2020 |
| Sharma Medical and Property Services Limited | Real estate | 2010 |
| Sharon Ayles Social Work Consultancy Limited | Health & social care | 2015 |
| Sharp Circle Properties Ltd | Real estate | 2024 |
| Sharp Talent Management Ltd | Professional & scientific | 2018 |
| Shaun Macklin Racing Limited | Arts & recreation | 2006 |
| Shaw Office Services Limited | Administrative & support | 2019 |
| Shaw Projects Limited | Real estate | 2024 |
| Shawbury Holdings Limited | Agriculture & fishing | 1989 |
| Shawn Tavares Ltd | Health & social care | 2010 |
| Shedfield House Estate Limited | Real estate | 2006 |
| Sheila Tarr Holdings Limited | Financial services | 2014 |
| Shelley Holdings Limited | Agriculture & fishing | 1982 |
| Shelley Supplies Ltd | Wholesale & retail | 2010 |
| Sherford Properties Limited | Construction | 1988 |
| Shibalance Limited | Professional & scientific | 2025 |
| Shivika Medical Ltd | Health & social care | 2013 |
| Shivsai Limited | Wholesale & retail | 2009 |
| Shoponline Limited | Wholesale & retail | 1999 |
| Shortcut Logistics Ltd | Transport & logistics | 2022 |
| Shrooms 2 U Ltd | Manufacturing | 2024 |
| SID (South) Ltd | Construction | 2022 |
| Sideways Marketing Limited | Professional & scientific | 2022 |
| Signal Post Consulting Ltd | Information & communication | 2023 |
| Sigur Housing Ltd | Real estate | 2021 |
| Silicon Dream Limited | Information & communication | 1993 |
| Silverwood Rise (Flats 12 & 14) Limited | Real estate | 2017 |
| Simcomm Academy Limited | Education | 2016 |
| Simmonds Consulting Services Ltd | Wholesale & retail | 2025 |
| Simple Essentials Limited | Wholesale & retail | 2005 |
| Simplefit Group Limited | Financial services | 2016 |
| Single Step Tours Limited | Administrative & support | 2012 |
| Sinister Arcus Limited | Information & communication | 2008 |
| Sisal Studio Limited | Manufacturing | 2025 |
| SIU Optometry Limited | Health & social care | 2025 |
| Sixth Formula Ltd | Education | 2023 |
| Sixth Level Marketing Limited | Other services | 2007 |
| SJH Anaesthetics Ltd | Health & social care | 2025 |
| SJL Country Services Limited | Agriculture & fishing | 2017 |
| SJP Independent Garage Specialist Limited | Wholesale & retail | 2011 |
| SJW Productions Limited | Arts & recreation | 2021 |
| Skadur Surgicals Ltd | Health & social care | 2024 |
| Skin Logic Romsey Ltd | Other services | 2025 |
| Skin Spa Limited | Other services | 2012 |
| Skin Squared Beauty Limited | Other services | 2017 |
| Sky Boxing Limited | Arts & recreation | 2016 |
| Skyesweets Ltd | Wholesale & retail | 2024 |
| Sleeping Trees Limited | Arts & recreation | 2021 |
| Small M Limited | Professional & scientific | 2010 |
| Smart Electrical Southern Limited | Construction | 2022 |
| Smarter Code Ltd | Information & communication | 2022 |
| Smartphones Ltd | Extraterritorial | 2014 |
| SME HR Consultancy Ltd | Professional & scientific | 2023 |