| Snazz the Edit Ltd | Information & communication | 2025 |
| Snbarfootbuilding Ltd | Construction | 2025 |
| Snow Trustees Limited | Administrative & support | 2003 |
| Snowbow Investments Limited | Financial services | 2026 |
| SNR Commercial Property Ltd | Other services | 2025 |
| SO Graphics Ltd | Information & communication | 2012 |
| SO41 Projects Limited | Real estate | 2025 |
| SO50 Ltd | Hospitality | 2024 |
| SO53X Interior Trim Ltd | Other services | 2019 |
| Society for Acute Medicine | Other services | 2011 |
| Soecology Limited | Professional & scientific | 2020 |
| Sofiscab Limited | Transport & logistics | 2023 |
| Soft Play Rocks Ltd | Administrative & support | 2022 |
| Softech Consultancy Limited | Information & communication | 2011 |
| Sohal Housing Ltd | Real estate | 2024 |
| Solar Marketing Limited | Administrative & support | 2011 |
| Solar Nebula Ltd | Construction | 2023 |
| Solar PV Partners Ltd | Construction | 2012 |
| Solaris IT Consulting Ltd. | Information & communication | 2017 |
| Solent Bricklaying Academy Limited | Education | 2025 |
| Solent Building and Development Ltd. | Construction | 1998 |
| Solent Electrical Services Limited | Construction | 1980 |
| Solent Enterprises Limited | Real estate | 2012 |
| Solent Estate Ltd | Real estate | 2013 |
| Solent Event Traffic Solutions Limited | Transport & logistics | 2025 |
| Solent Executive Chauffeurs Ltd | Transport & logistics | 2026 |
| Solent Flight Limited | Arts & recreation | 1997 |
| Solent Media Services Ltd | Information & communication | 2026 |
| Solent Powder Finishers Limited | Manufacturing | 1982 |
| Solent Property Group Limited | Real estate | 2025 |
| Solent Property Holdings Limited | Real estate | 2019 |
| Solent Retail Limited | Wholesale & retail | 2023 |
| Solent Road Markings (Southern) Limited | Construction | 2002 |
| Solent Youth Action | Professional & scientific | 2004 |
| Solent-Pages Limited | Professional & scientific | 2025 |
| Solkoru Ltd | Wholesale & retail | 2023 |
| Solo Sensei Ltd | Professional & scientific | 2013 |
| Solvr Digital Ltd | Information & communication | 2025 |
| Somerset Avenue Local Centre Management Company Limited | Real estate | 2015 |
| Sophcob Limited | Professional & scientific | 2018 |
| Sophia's House Limited | Health & social care | 2014 |
| Sorin&Co Limited | Transport & logistics | 2019 |
| SOS Property Care Ltd | Construction | 2019 |
| Sotwebsolutions Limited | Professional & scientific | 2025 |
| Soundscape Creative Ltd | Professional & scientific | 2023 |
| Sourcecube Ltd | Information & communication | 2017 |
| South Central Fire and Rescue Service Ltd | Public administration | 2025 |
| South Coast Actuarial Services Ltd | Financial services | 2014 |
| South Coast Autocare Limited | Wholesale & retail | 2026 |
| South Coast Candy Ltd | Hospitality | 2018 |
| South Coast Custom Campers Ltd | Wholesale & retail | 2018 |
| South Coast Electrical Testing Ltd | Professional & scientific | 2015 |
| South Coast Freight Ltd | Transport & logistics | 2019 |
| South Coast Landscape and Gardening Ltd | Construction | 2025 |
| South Dale Court Management Company Limited | Households | 1985 |
| South Down Cars Ltd | Wholesale & retail | 2020 |
| South East Ceramics Limited | Construction | 2006 |
| South Midlands Communications Limited | Manufacturing | 1958 |
| South West Tank Supplies Ltd | Water & waste | 2021 |
| Southampton & District Motor Cycle Club | Arts & recreation | 2004 |
| Southampton Anaesthetic Service LLP | | 2019 |
| Southampton Arts Academy Limited | Arts & recreation | 2014 |
| Southampton Chauffeurs Limited | Transport & logistics | 2015 |
| Southampton Counselling and Therapy Centre Limited | Health & social care | 1995 |
| Southampton DAB C.I.C. | Information & communication | 2024 |
| Southampton Groundworks Ltd | Construction | 2025 |
| Southampton Holdings Ltd | Real estate | 2020 |
| Southampton Property Developments Limited | Construction | 2008 |
| Southampton Roof Repairs Ltd | Construction | 2026 |
| Southampton Trophies & Engraving Limited | Wholesale & retail | 2017 |
| Southdown Place Management Company Limited | Households | 2008 |
| Southern Air Services and Hire Limited | Administrative & support | 2024 |
| Southern Air Systems Limited | Manufacturing | 2001 |
| Southern Cafe Limited | Hospitality | 2022 |
| Southern Corporate Services Limited | Extraterritorial | 2000 |
| Southern Creative Communities CIC | Education | 2023 |
| Southern Drainage Services Ltd | Administrative & support | 2012 |
| Southern GAS Safe Ltd | Construction | 2009 |
| Southern Industrial Doors Ltd | Construction | 2009 |
| Southern Landscape Contracts Limited | Administrative & support | 2012 |
| Southern Lifting Services Limited | Construction | 2023 |
| Southern Living England Limited | Construction | 2026 |
| Southern Precast Installations Limited | Construction | 2021 |
| Southern Sales & Services Limited | Manufacturing | 1995 |
| Southern Snooker Ltd | Arts & recreation | 2017 |
| Southern Stone & Tools Ltd | Manufacturing | 2024 |
| Southraw Limited | Wholesale & retail | 2024 |
| Southwest Data Cables Limited | Professional & scientific | 1998 |
| Sovereign Data Foundry Ltd | Information & communication | 2026 |
| Sovereignty Healthcare Limited | Administrative & support | 2023 |
| Sozo Systems Limited | Manufacturing | 2015 |
| So’Dol Cleaning Service Ltd | Administrative & support | 2021 |
| Spacestories Design Collective Limited | Professional & scientific | 2022 |
| Sparkle and Shine Eastleigh Limited | Administrative & support | 2022 |
| Sparks Ellison Limited | Real estate | 2002 |
| SPC Bathrooms Ltd | Construction | 2015 |
| Spear Freight Limited | Transport & logistics | 2022 |
| Spearhead Security Ltd | Administrative & support | 2026 |
| Special Forces Security Limited | Administrative & support | 2020 |
| Special Gelato Ltd | Hospitality | 2017 |