| Spiral Holdings Limited | Financial services | 2006 |
| Spiral Staircase Systems Limited | Professional & scientific | 1992 |
| Spitfire AA810 Restoration Ltd | Manufacturing | 2018 |
| Splash in a Pond Ltd. | Information & communication | 2015 |
| Splendid Things Consulting Limited | Information & communication | 2015 |
| SPRING77 Food Ltd | Hospitality | 2024 |
| Springham Grove LLP | | 2020 |
| Springles Farm Holdings Ltd | Financial services | 2024 |
| Springles Farm Limited | Agriculture & fishing | 2020 |
| Square Hole Productions Limited | Administrative & support | 2008 |
| Ssec Epos Company Limited | Wholesale & retail | 2017 |
| ST Events Catering Ltd | Hospitality | 2024 |
| ST. Georges Management Company Limited | Households | 1997 |
| ST. Johns (Southern) Partnership LLP | | 2007 |
| ST. Ledger Ltd | Professional & scientific | 2025 |
| ST. Pancras Stores Limited | Wholesale & retail | 2013 |
| Stand Sure Solutions Ltd | Information & communication | 2024 |
| Standpoint Earth CIC | Professional & scientific | 2022 |
| Stanley Strategic Consultants LLP | | 2023 |
| Stansfield Technical Services Limited | Information & communication | 2007 |
| Stapleton Consulting Limited | Professional & scientific | 2011 |
| Star Community Pottery CIC | Arts & recreation | 2024 |
| Starfield Productions Limited | Information & communication | 1991 |
| Starfish Youth Music Community Interest Company | Arts & recreation | 2011 |
| Starpoint Ltd. | Wholesale & retail | 2015 |
| State Lite Limited | Wholesale & retail | 2019 |
| Staverton Nursery Limited | Agriculture & fishing | 2013 |
| Stephen Vokins Limited | Wholesale & retail | 1996 |
| Stepping Stones, Lewes Community Nursery Ltd | Education | 2012 |
| Sterling Commercial Maintenance Limited | Construction | 2003 |
| Steven Mooney Machinery Limited | Wholesale & retail | 2005 |
| Stevylee Ltd | Manufacturing | 2025 |
| Stirring the POT Limited | Hospitality | 2020 |
| STJ E-Build Limited | Construction | 2025 |
| Stnsb Investments Limited | Real estate | 2025 |
| Stockwell Court Residents Association Limited | Real estate | 1979 |
| Stoke Newington Slindon Ltd | Real estate | 2009 |
| STOP2RIDE Ltd | Information & communication | 2024 |
| Stormwind Holdings Ltd | Wholesale & retail | 2024 |
| Strategic Technology Initiatives Limited | Information & communication | 1990 |
| Stratum Digital Ltd | Information & communication | 2025 |
| Streams Properties Ltd | Real estate | 2020 |
| STREAMS4E Limited | Education | 2020 |
| Street Art Initiative - Lewes (Sail) Community Interest Company | Other services | 2024 |
| Street Kitchens Event Hire Ltd | Hospitality | 2025 |
| Strong Consulting Limited | Professional & scientific | 2026 |
| STU2U Ltd | Extraterritorial | 2020 |
| Studio Amos LLP | | 2021 |
| Studio Bates RAI Ltd | Professional & scientific | 2020 |
| Studio Creativo Ltd | Professional & scientific | 2020 |
| Studio FLO Interiors Ltd | Wholesale & retail | 2022 |
| Studio Thoughtcraft Ltd | Professional & scientific | 2019 |
| STUDIO303 South Ltd | Professional & scientific | 2021 |
| Stupid EGG Limited | Wholesale & retail | 2019 |
| Sturdy Foundations (GB) Ltd | Real estate | 2020 |
| Stych Accessories Limited | Extraterritorial | 2020 |
| Stych Limited | Extraterritorial | 2020 |
| Style and Space Contractors Ltd | Construction | 2011 |
| Styles Field Management Company Limited | Households | 2018 |
| SUL Books Ltd | Information & communication | 2024 |
| Summit Environmental Ltd | Professional & scientific | 2018 |
| Sun Rose Care Limited | Health & social care | 2014 |
| Supaphoto Limited | Information & communication | 2003 |
| Super Visual Ltd | Professional & scientific | 2026 |
| Supereo Ltd | Information & communication | 2023 |
| Superfun Happy Pizza Time Limited | Hospitality | 2021 |
| Superfuzz Ltd | Hospitality | 2020 |
| Superglue Limited | Arts & recreation | 2013 |
| Support Your Mind Ltd | Health & social care | 2026 |
| Surveillance Studies Network | Professional & scientific | 2006 |
| Susa Jewellery Ltd | Manufacturing | 2017 |
| Sussex Accounting Solutions Limited | Professional & scientific | 2011 |
| Sussex Community Foundation | Public administration | 2006 |
| Sussex Eats Ltd | Hospitality | 2025 |
| Sussex Engineering Ltd | Manufacturing | 2011 |
| Sussex Floor Restoration Ltd | Construction | 2019 |
| Sussex Grange Furniture Limited | Manufacturing | 2014 |
| Sussex Hospitality Services Limited | Hospitality | 2011 |
| Sussex Medical Services Limited | Health & social care | 2019 |
| Sussex New Builds Ltd | Construction | 2018 |
| Sussex Past Trading Ltd. | Arts & recreation | 1997 |
| Sussex Payroll Services Limited | Administrative & support | 2010 |
| Sussex Plumbing and Heating Limited | Construction | 2018 |
| Sussex Prostate Oncology Ltd | Health & social care | 2024 |
| Sussex Rural Community Council | Health & social care | 1994 |
| Sussex Scuff Repair Ltd | Wholesale & retail | 2023 |
| Sussex Sports Cars Limited | Wholesale & retail | 1999 |
| Sussex Steel Stockholders Ltd | Construction | 2015 |
| Sussex Studios Limited | Administrative & support | 2018 |
| Sussex Wine Producers | Other services | 2017 |
| Sustainability Managers for Schools C.I.C. | Education | 2023 |
| Swag BAG Games Limited | Information & communication | 2025 |
| Swanborough Lodges Limited | Hospitality | 2018 |
| Sweet Treasures Limited | Hospitality | 2019 |
| SWIM2WIN Limited | Arts & recreation | 2020 |
| Switched on Brighton Limited | Professional & scientific | 2012 |
| Swtch Ltd | Wholesale & retail | 2016 |
| Sylvan Limited | Professional & scientific | 2015 |
| Symposium Fine Wine Emporium LLP | | 2009 |
| Synergy Electrical Sussex Ltd | Construction | 2025 |