| Solo Electrical (South) Limited | Construction | 2023 |
| Solo Electrical UK Limited | Construction | 2008 |
| Solow Flooring Contractors Limited | Construction | 2005 |
| Solstice Wellbeing Limited | Extraterritorial | 2020 |
| Soltanee Ltd | Transport & logistics | 2025 |
| Soltani Real Estate Ltd | Real estate | 2025 |
| Soltech Development Services Limited | Information & communication | 2013 |
| Soltero UK Ltd | Wholesale & retail | 2021 |
| Soluca Real Estate Consultancy Limited | Professional & scientific | 2018 |
| Solution Originale Ltd | Real estate | 2011 |
| SOLUTIONS4ENTERPRISE.BIZ Limited | Professional & scientific | 2003 |
| Solveig + Montealegre Limited | Professional & scientific | 2023 |
| Solverapid Limited | Wholesale & retail | 2002 |
| Solvere Property Services Limited | Real estate | 2012 |
| SOM Noor Ltd | Administrative & support | 2019 |
| Soma Wanti Ltd | Households | 2022 |
| Somarville Harmes Limited | Administrative & support | 2004 |
| Somborne Court (Southampton) Limited | Real estate | 2009 |
| Somborne Partnership Ltd | Agriculture & fishing | 2021 |
| Somerscales Services Limited | Professional & scientific | 2021 |
| Somerset Capital Management Limited | Administrative & support | 2007 |
| Somerset Court (Southampton) Management Company Limited | Households | 1996 |
| Somerstown Tavern Limited | Hospitality | 2009 |
| Something Floral Ltd | Wholesale & retail | 2013 |
| Sommerville Turpin Holdings Limited | Financial services | 2021 |
| Sommerville Turpin Limited | Real estate | 2004 |
| Sommerville Turpin Properties Limited | Real estate | 2021 |
| Somnium INV Group Ltd | Information & communication | 2025 |
| Somnium Investments 25 Ltd | Manufacturing | 2025 |
| Somnium Investments Limited | Real estate | 2016 |
| Somnium L2R Investments Ltd | Real estate | 2025 |
| Somnium Sales and Marketing Ltd | Information & communication | 2025 |
| Soms Digital Ltd | Information & communication | 2018 |
| Songbird Entertainment Ltd | Education | 2020 |
| Soniya Limited | Wholesale & retail | 2010 |
| Sonoview Ltd | Health & social care | 2010 |
| Sonrise Healthcare Limited | Public administration | 2023 |
| Sooba Medical Limited | Manufacturing | 2020 |
| Sook Retail Limited | Wholesale & retail | 2019 |
| Soothills Bakeries Limited | Financial services | 2001 |
| Soothills Limited | Manufacturing | 1965 |
| Sophi Luxury Glamour Ltd | Administrative & support | 2025 |
| Sophie James Aesthetics Ltd | Other services | 2023 |
| Sophie Karl Production Ltd | Information & communication | 2018 |
| Sora Patisserie Limited | Hospitality | 2020 |
| Sore DE Ltd | Hospitality | 2024 |
| Sorm Limited | Mining & quarrying | 2019 |
| Soroast Cafes Ltd | Hospitality | 2023 |
| Soroast Ltd | Manufacturing | 2015 |
| Sorooted Foods UK Ltd | Manufacturing | 2024 |
| Sorrento Clinic Ltd | Health & social care | 2024 |
| Sortep Ltd | Information & communication | 2026 |
| SOS Data Comms Ltd | Construction | 2018 |
| SOS Safety Ltd | Professional & scientific | 2016 |
| SOS Self Storage Ltd | Transport & logistics | 2016 |
| Soter Safety Consulting Limited | Professional & scientific | 2021 |
| Soton Car Parts Limited | Wholesale & retail | 2015 |
| Soton Cars Limited | Transport & logistics | 2023 |
| Soton Cars Southamoton Taxis Limited | Transport & logistics | 2026 |
| Soton Cars Southampton Ltd | Transport & logistics | 2016 |
| Soton Cleaning Services Ltd | Wholesale & retail | 2018 |
| Soton Construction Ltd | Construction | 2018 |
| Soton Darts Ltd | Wholesale & retail | 2026 |
| Soton Dynamics Ltd | Information & communication | 2021 |
| Soton Eagles Youth FC Limited | Arts & recreation | 2019 |
| Soton Electrical Ltd | Construction | 2024 |
| Soton Fried Chicken Limited | Hospitality | 2024 |
| Soton Grill Ltd | Hospitality | 2026 |
| Soton Hydrodynamics Ltd | Professional & scientific | 2020 |
| Soton Lettings Limited | Real estate | 2014 |
| Soton Property Management Ukeig | | 2013 |
| Soton Tech Ltd | Wholesale & retail | 2023 |
| Soton Tree Care Ltd | Agriculture & fishing | 2025 |
| Soton Tyres Limited | Wholesale & retail | 2023 |
| Soton.K.H Ltd | Hospitality | 2026 |
| Sotonride Ltd | Transport & logistics | 2026 |
| Sotonsparkle Limited | Administrative & support | 2026 |
| Sotton Music Services Ltd | Arts & recreation | 2025 |
| SOU Access Ltd | Construction | 2024 |
| Soudabeh Heidari Ltd | Wholesale & retail | 2025 |
| Soul Retreats Limited | Arts & recreation | 2015 |
| Soul Surf Coach Ltd | Arts & recreation | 2019 |
| Souliuservices Ltd | Transport & logistics | 2010 |
| Sound Advice Acoustics Limited | Professional & scientific | 2003 |
| Sound Code Limited | Information & communication | 2015 |
| Sound POP Academy Limited | Arts & recreation | 2018 |
| Soundfish Limited | Information & communication | 2017 |
| Sounds Professional Ltd | Administrative & support | 2016 |
| Soundvault Limited | Information & communication | 2008 |
| Source & Connect Ltd | Administrative & support | 2023 |
| Sousa Law Limited | Professional & scientific | 2016 |
| Souter Estates Ltd | Real estate | 2023 |
| South Airport Taxis Limited | Transport & logistics | 2024 |
| South Auto Repairs and MOT Centre Ltd | Manufacturing | 2020 |
| South Body Repairs Ltd | Wholesale & retail | 2023 |
| South Catering Express Ltd | Hospitality | 2023 |
| South Central Properties Ltd | Real estate | 2024 |
| South Chickenland Limited | Hospitality | 2021 |
| South City Electrical Limited | Construction | 2005 |
| South Coast Aggregates Limited | Construction | 2021 |