| Silver Thatch Stables Ltd | Agriculture & fishing | 2021 |
| Silverdale Woodlands Limited | Extraterritorial | 2016 |
| Simon Ashen Limited | Information & communication | 2015 |
| Simon Birch Music Ltd | Information & communication | 2015 |
| Simon Davis Art Direction Limited | Information & communication | 2010 |
| Simon Dent Management Limited | Professional & scientific | 2014 |
| Simon Eldon Photography Limited | Professional & scientific | 2015 |
| Simon Murray Limited | Health & social care | 2002 |
| Simon Scott Landscaping Ltd | Administrative & support | 2012 |
| Simple BMS Limited | Professional & scientific | 2023 |
| Simple Building Safety Limited | Professional & scientific | 2024 |
| Simple Life Safety Systems Limited | Professional & scientific | 2023 |
| Simple Special Projects Limited | Professional & scientific | 2023 |
| Simple Suppression Systems Limited | Professional & scientific | 2024 |
| Simply Hair Sussex Limited | Other services | 2007 |
| Simpson House (104 Marine Parade) Limited | Households | 2015 |
| Simpsons Health Foods Limited | Wholesale & retail | 2008 |
| Simro Holdings LLP | | 2026 |
| Sinclair & Sons Ltd | Professional & scientific | 2019 |
| Singular Mars Limited | Professional & scientific | 2017 |
| Sirah Developments Limited | Professional & scientific | 2007 |
| SIX Five Digital Ltd | Professional & scientific | 2020 |
| SJ Management Ltd | Real estate | 2022 |
| SJ Medical Services Limited | Health & social care | 2025 |
| SJ Navas Ltd | Professional & scientific | 2022 |
| SJF Accounting & Tax Ltd | Professional & scientific | 2015 |
| SJH Building Co. Ltd | Construction | 2018 |
| SJH Services Limited | Information & communication | 2024 |
| SJS Van Hire Limited | Administrative & support | 2001 |
| Skylift Facilities Ltd | Construction | 2026 |
| Slipstream Projects Limited | Professional & scientific | 2025 |
| Slot Machine Theatre Company Limited | Arts & recreation | 2013 |
| SM Trimming Ltd | Wholesale & retail | 2026 |
| Smallstuff Accessories Limited | Extraterritorial | 2020 |
| Smallworld Accessories Holdings Limited | Wholesale & retail | 2016 |
| Smallworld Accessories Limited | Wholesale & retail | 2016 |
| Smart Future Group Limited | Information & communication | 2019 |
| Smigeon Limited | Hospitality | 2021 |
| Smile Savers Hungary Limited | Professional & scientific | 2004 |
| Smith and Jakes Limited | Manufacturing | 2015 |
| Smith FOX Ltd | Professional & scientific | 2020 |
| Snake River Press Limited | Information & communication | 2005 |
| Snap Events Limited | Administrative & support | 2010 |
| SNB Consultancy Ltd | Professional & scientific | 2023 |
| Snickers UK Ltd | Wholesale & retail | 2017 |
| Snickersuk.Com Ltd | Extraterritorial | 2010 |
| Soapbox Creative Limited | Administrative & support | 2008 |
| Softer + Wild Ltd | Manufacturing | 2016 |
| Software Hothouse Ltd | Information & communication | 2003 |
| Some ARE More Equal Fabrications Ltd | Manufacturing | 2026 |
| Somersault Strategy Limited | Professional & scientific | 2012 |
| Somnovum Ltd | Health & social care | 2026 |
| Sonar Holdings Ltd | Information & communication | 2024 |
| Sondering Souls Limited | Health & social care | 2024 |
| Songbooks & Accounts Ltd | Professional & scientific | 2020 |
| Sonic Boom Audio Limited | Information & communication | 2002 |
| Sonofthesea Ltd | Hospitality | 2022 |
| Sorrel Carmichael Properties Limited | Real estate | 2025 |
| Soulfit Limited | Arts & recreation | 2017 |
| Sound System Design Limited | Information & communication | 2002 |
| Source Stream Ltd | Information & communication | 2015 |
| South Brockwells Farm School Ltd | Education | 2023 |
| South Downs Cider Limited | Manufacturing | 2018 |
| South Downs Commercial and Domestic Maintenance Limited | Construction | 2018 |
| South Downs Forest School C.I.C. | Education | 2020 |
| South Downs Homecare Ltd | Professional & scientific | 2024 |
| South Downs Incorporated Ltd | Wholesale & retail | 2023 |
| South Downs Learning Ltd | Education | 2026 |
| South Downs Site Investigation Ltd | Construction | 2025 |
| South Downs Sweep Ltd | Administrative & support | 2023 |
| South East Landbased Training Courses LLP | | 2020 |
| South East Wood Fuels Ltd | Other services | 2004 |
| South Street Bonfire Society Limited | Other services | 1997 |
| South Street Events Ltd | Hospitality | 2013 |
| South Way Consultancy Limited | Information & communication | 2012 |
| Southdown Bars Ltd | Hospitality | 2020 |
| Southdown Trading Ltd | Arts & recreation | 2026 |
| Southease Press Ltd | Manufacturing | 2024 |
| Southerham Services Limited | Water & waste | 1998 |
| Southern Cabling Limited | Information & communication | 2007 |
| Southern Car Sales Limited | Wholesale & retail | 2010 |
| Southern Comfort Limited | Manufacturing | 2003 |
| Southern Lights Filming Ltd | Construction | 2023 |
| Southern Platforms Ltd | Construction | 2019 |
| Southern Radiology Limited | Health & social care | 2024 |
| Southern Spice House Ltd | Hospitality | 2024 |
| Southern Stairlifts Limited | Wholesale & retail | 2020 |
| Southern Wellness Action Group CIC | Health & social care | 2021 |
| Southover Bonfire Society Limited | Other services | 2006 |
| Southover Management Company Limited | Real estate | 2006 |
| Southover Manor General Educational Trust Limited | Health & social care | 1988 |
| Southsea Investment Services Limited | Financial services | 1964 |
| Soylu Maintenance Ltd | Construction | 2019 |
| SP Consulting Services Ltd | Professional & scientific | 2004 |
| Spark Circles CIC | Health & social care | 2026 |
| Sparrowworks Limited | Professional & scientific | 2010 |
| Special OPS Inc Ltd | Arts & recreation | 2023 |
| Spencer MAY Commercial LLP | | 2020 |
| Sphereverse Ltd | Information & communication | 2021 |
| Spice Island Imports Ltd | Extraterritorial | 2024 |