| Shaw Packaging Services Limited | Administrative & support | 2003 |
| Shaw Stone Limited | Manufacturing | 2003 |
| Shawmax Limited | Administrative & support | 2002 |
| Sheila Tarr Limited | Financial services | 2004 |
| Shelter Environmental Ltd | Other services | 2019 |
| Shipway Garden Contractors Limited | Administrative & support | 1999 |
| Shirley Garage Limited | Wholesale & retail | 2005 |
| Shiv Jyot Limited | Wholesale & retail | 2025 |
| Shoantel Limited | Information & communication | 2002 |
| SHOPONLINE4U Ltd | Wholesale & retail | 2019 |
| Shorelands Court Residents Association Limited | Households | 1986 |
| Shot by Shot Limited | Information & communication | 2007 |
| Sibley-Hale Scenic Carpentry Ltd | Administrative & support | 2001 |
| Sign TEC Graphics & Signs Ltd | Professional & scientific | 1998 |
| Signal Locker Limited | Manufacturing | 2004 |
| Signs and Lines Limited | Wholesale & retail | 2006 |
| Silclear Limited | Manufacturing | 1987 |
| Simeon Morgan Farming Limited | Agriculture & fishing | 2007 |
| Simon Austin Services Ltd | Wholesale & retail | 2004 |
| Simon Frampton Limited | Construction | 2002 |
| Simon Robinson (Shipbroking) Limited | Transport & logistics | 1989 |
| Simple Buzz UK Ltd | Wholesale & retail | 2023 |
| Simply Alpine Ltd | Professional & scientific | 2005 |
| Simplyadi Ltd | Information & communication | 2026 |
| Singleace Limited | Agriculture & fishing | 1997 |
| Sjbwinebar Ltd | Hospitality | 2012 |
| SJE Property Limited | Construction | 2005 |
| Skibike Ltd | Wholesale & retail | 2001 |
| Skoolkit Limited | Wholesale & retail | 1973 |
| SKU Logistics Limited | Transport & logistics | 2011 |
| Skylark Rise Limited | Extraterritorial | 2007 |
| Skytech Aviation Services Limited | Administrative & support | 1993 |
| Slate and Gold Limited | Hospitality | 2019 |
| Sleipner Motor Ltd | Wholesale & retail | 2004 |
| Slick Images Limited | | 1983 |
| Smart Card Shop Limited | Professional & scientific | 1999 |
| Smart Logic Limited | Professional & scientific | 2002 |
| Smith & Austin Engineering Products Limited | Manufacturing | 1971 |
| Smith Bradbeer & Company Limited | Wholesale & retail | 1892 |
| Smoores Supplies Ltd | Information & communication | 2006 |
| Smoumc Limited | Wholesale & retail | 2026 |
| Smutils Limited | Information & communication | 1999 |
| Snow and Trek Limited | Administrative & support | 2005 |
| Softsense Limited | Information & communication | 2004 |
| Sogeclair Aerospace Limited | Professional & scientific | 2005 |
| Soknak Media Ltd | Information & communication | 2025 |
| Soledo Engineering Limited | | 1985 |
| Solent Builders Limited | Construction | 2004 |
| Solent Business Angels Limited | Construction | 1996 |
| Solent Ceramics Limited | Construction | 2003 |
| Solent Healthcare Limited | Health & social care | 2013 |
| Solent Industrial Estates Limited | Real estate | 1971 |
| Solent Nominees Limited | Administrative & support | 2007 |
| Solent Pipelaying Services Ltd | Extraterritorial | 1997 |
| Solent Trusses Limited | Manufacturing | 1993 |
| Sollas UK Limited | Administrative & support | 1991 |
| Solva Technologies Limited | Information & communication | 1990 |
| Somerford Business Park Management Company Limited | Real estate | 1989 |
| Source International Limited | Professional & scientific | 1988 |
| Sourcesolar Limited | Professional & scientific | 1998 |
| South Downs Capital Limited | Professional & scientific | 2001 |
| South Hampshire Assurance Services (Investments) Limited | | 1981 |
| South Hants Garage Services Limited | Wholesale & retail | 2003 |
| South Road Limited | Households | 2006 |
| South West Digital Radio Limited | Professional & scientific | 2002 |
| Southam Tyres Limited | Extraterritorial | 2001 |
| Southampton Car Clinic Limited | Transport & logistics | 1995 |
| Southampton Isle of Wight and South of England Royal Mail Steam Packet Company Limited | Transport & logistics | 1861 |
| Southampton Mencap | Administrative & support | 2003 |
| Southampton Property Services Limited | Real estate | 2004 |
| Southern Aerial (Communications) Limited | Construction | 1981 |
| Southern Blasting Services Limited | Professional & scientific | 2006 |
| Southern Bridges | Health & social care | 2005 |
| Southern Cross Precision Engineering Limited | Extraterritorial | 1969 |
| Southern Dental Laboratories Limited | Health & social care | 2002 |
| Southern Springs and Pressings Limited | Administrative & support | 1948 |
| Southern Woodland Products Limited | Agriculture & fishing | 2005 |
| Southrope Developments Limited | Construction | 1990 |
| Southsea Deckchairs Limited | Wholesale & retail | 2001 |
| Southsea Village (Management) Limited | Households | 2025 |
| Southwest Trucks Limited | Wholesale & retail | 2003 |
| Spaceware Ltd | Professional & scientific | 2006 |
| Spain House Management Ltd | Households | 2003 |
| Special FX Solutions LLP | | 2007 |
| Spence Properties Limited | Real estate | 1998 |
| Spinningdrum Limited | Administrative & support | 2008 |
| Spring Board Sholing Limited | Real estate | 2003 |
| Spring Court Management Company Limited | Households | 1988 |
| SPS International Limited | Administrative & support | 2007 |
| ST. Cross Holdings Limited | Professional & scientific | 2005 |
| ST. George Mineral Water Company Limited | Professional & scientific | 1997 |
| Stadclip Limited | Information & communication | 1983 |
| Standard House Limited | Financial services | 2006 |
| Stansted Park Events Limited | Arts & recreation | 1997 |
| Star Financial (UK) Limited | Financial services | 2006 |
| Starjammer Engineering Limited | Information & communication | 2003 |
| Starwheel Loyalty Solutions Ltd | Administrative & support | 2024 |
| Starwise Property Limited | Real estate | 1998 |
| Steam Engineering Ltd | Professional & scientific | 2006 |
| Steffral Limited | Professional & scientific | 2005 |