| Slack Group Holdings Limited | Financial services | 2025 |
| SLB Properties (Sussex) Limited | Real estate | 2018 |
| Slim Spirits Ltd | Wholesale & retail | 2020 |
| Slimline Wine Limited | Wholesale & retail | 2017 |
| SLS Fabrications Limited | Manufacturing | 1996 |
| SMA Lofts & Extension Ltd | Construction | 2025 |
| SMA Lofts Ltd | Construction | 2024 |
| Smart Choice Wholesalers Ltd | Wholesale & retail | 2021 |
| Smart Landscapes Limited | Professional & scientific | 2024 |
| Smart Materials and Devices Limited | Professional & scientific | 2015 |
| Smerdal Ltd | Real estate | 2018 |
| Smerdal Property Services Ltd | Administrative & support | 2022 |
| Smile Financial Life Planning Limited | Professional & scientific | 2024 |
| Smith & Baker Limited | Other services | 2010 |
| Smmw Holdings Limited | Financial services | 2020 |
| SMS Ice Rinks Ltd | Arts & recreation | 2025 |
| Smvdl 1 Limited | Real estate | 2025 |
| Smvdl 2 Limited | Real estate | 2025 |
| Smvdl 3 Limited | Real estate | 2025 |
| SMY (2022) Ltd | Administrative & support | 2013 |
| Smyle Creative Group Limited | Financial services | 2018 |
| Smyle Creative Limited | Administrative & support | 2007 |
| Smyle Events Limited | Arts & recreation | 2003 |
| Smyle Productions Ltd | Extraterritorial | 2001 |
| Snow LAB UK Ltd | Wholesale & retail | 2006 |
| SNP Associates Limited | Professional & scientific | 2011 |
| SO Saucy Authentic Thai Sauces Ltd | Manufacturing | 2017 |
| Socialsand Ltd | Other services | 2024 |
| Soft Tissue Therapy Limited | Health & social care | 2018 |
| Sojo Provisions Limited | Real estate | 2021 |
| Solar Solve Limited | Manufacturing | 1988 |
| Solec Renewables Limited | Construction | 2023 |
| Solteqh Healthcare Management Ltd | Professional & scientific | 2013 |
| Something for Everyone Ltd | Wholesale & retail | 2018 |
| Sonn Studio Limited | Professional & scientific | 2024 |
| Sono Solutions Ltd | Construction | 2017 |
| Sophia Louise Knight Limited | Administrative & support | 2014 |
| Soundreach Limited | Professional & scientific | 2025 |
| South Care Homes Ltd | Health & social care | 2017 |
| South Cliff Properties LLP | | 2022 |
| South Close Residents Association Limited | Households | 1995 |
| South Coast Marketing Collective Ltd | Information & communication | 2023 |
| South Downs Cleaning Limited | Administrative & support | 2021 |
| South East Coast Property Developments Ltd | Extraterritorial | 2024 |
| South East Development Services Ltd | Professional & scientific | 2023 |
| South East Groundcare Machinery Limited | Manufacturing | 2010 |
| South East Leisure Ltd | Hospitality | 2023 |
| South East Marts Limited | Wholesale & retail | 1978 |
| South East Solar and Storage Limited | Construction | 2023 |
| South East Welding Limited | Administrative & support | 2003 |
| South England Tyre Service Limited | Extraterritorial | 1968 |
| Southdown Food Supplies Limited | Wholesale & retail | 2015 |
| Southdown Security Services Ltd | Administrative & support | 2014 |
| Southern Boat Salvage Limited | Manufacturing | 2026 |
| Southern Eggs Ltd | Wholesale & retail | 2021 |
| Southern Site Welding Limited | Professional & scientific | 2020 |
| Southern Sports Media Ltd | Professional & scientific | 2025 |
| Southern Steelwork and Cladding Ltd | Construction | 2020 |
| Southern Sterilizer & Decontamination Consultancy Ltd | Administrative & support | 2018 |
| Southern Stores (2015) Limited | Wholesale & retail | 2015 |
| Southwark Property Services & Investment Limited | Real estate | 2013 |
| Sovereign Financial Limited | Financial services | 2008 |
| Sovereign Holdings (Developments) Limited | Professional & scientific | 2004 |
| Sovereign Litigation Management Limited | Financial services | 2015 |
| SP Medhurst Construction & Management Services Limited | Professional & scientific | 2001 |
| Spectre Print Limited | Other services | 2011 |
| Speedwell Catering Hire Limited | Administrative & support | 2011 |
| Sphark Ltd | Wholesale & retail | 2025 |
| Spiral Sounds Limited | Information & communication | 2024 |
| Spirit Level Services Limited | Construction | 2003 |
| Splj Knight Properties LLP | | 2022 |
| Spotlight HR Consultants Limited | Administrative & support | 2019 |
| Springs Investment Group Limited | Real estate | 2023 |
| Squid Media Limited | Administrative & support | 2024 |
| ST Bede's School Trust Sussex | Education | 1978 |
| ST Johns Servicing Limited | Wholesale & retail | 2024 |
| ST Mary's View Developments Limited | Real estate | 2022 |
| ST Raphael’S Urology Ltd | Health & social care | 2026 |
| ST. Leonards Test Centre Limited | Wholesale & retail | 2001 |
| Stacked Spin Ltd | Other services | 2019 |
| Stafford Avondale Ltd | Real estate | 2020 |
| Standen Associates Limited | Professional & scientific | 2003 |
| Star 1 Movies Ltd | Construction | 2023 |
| Starfish Pictures Limited | Arts & recreation | 2011 |
| Stark Interiors Ltd | Construction | 2021 |
| Starkline Capital Limited | Real estate | 2025 |
| State 8 Training Limited | Extraterritorial | 2023 |
| Station Road Hellingly Management Limited | Households | 2022 |
| Staubyn Tree Consultancy Ltd | Professional & scientific | 2018 |
| Stay & Hobbs Ltd | Professional & scientific | 2022 |
| Stellar Distribution Ltd | Transport & logistics | 2025 |
| Stephen Lawson Limited | Professional & scientific | 2011 |
| Stephen Wilson Partnership Limited | Construction | 2001 |
| Stephen Woodley Heating & Plumbing Limited | Construction | 2008 |
| Stepnage OS Limited | Information & communication | 2025 |
| Steve Bull Limited | Manufacturing | 2008 |
| Steve Derham Limited | Wholesale & retail | 2010 |
| Steven Bray Limited | Households | 2008 |
| Stevens & Carter Limited | Real estate | 2004 |
| Stevens R Limited | Wholesale & retail | 2015 |