| Steershearne Consulting Ltd | Professional & scientific | 2024 |
| Stellar Electromagnetics Ltd | Professional & scientific | 2023 |
| Steve Lovell Limited | Professional & scientific | 2023 |
| Steve Moger (Carpets & Vinyl) Limited | Construction | 2002 |
| Steven Green Limited | Administrative & support | 2019 |
| Stogdale ST James Ltd | Administrative & support | 2016 |
| Stonecott Close Management Company Limited | Households | 1988 |
| Strat-Edgee Ltd | Transport & logistics | 2025 |
| Strategic Planning Ltd | Professional & scientific | 2000 |
| Strathblaine Properties Limited | Real estate | 2009 |
| Stroods Limited | Administrative & support | 2010 |
| Summerheath Estates Ltd | Construction | 2015 |
| Sunset Properties Limited | Real estate | 2016 |
| Superior Glass Limited | Construction | 2003 |
| Supportiveproperties Ltd | Real estate | 2024 |
| Sureflow Solutions Ltd | Construction | 2009 |
| Susan Lake Lighting Design Limited | Professional & scientific | 2016 |
| Sussex Apothecary Limited | Wholesale & retail | 1999 |
| Sussex Automotive Centres Limited | Wholesale & retail | 2017 |
| Sussex Chef Limited | Hospitality | 2017 |
| Sussex Chelonian Society Ltd | Other services | 2025 |
| Sussex Dry-Lining Limited | Construction | 1980 |
| Sussex Environmental Solutions Ltd | Administrative & support | 2025 |
| Sussex Fayre Ltd | Manufacturing | 2011 |
| Sussex Gate Services LLP | | 2017 |
| Sussex Home Vets Ltd | Professional & scientific | 2023 |
| Sussex Notary Limited | Professional & scientific | 2026 |
| Sussex Saddlery Limited | Administrative & support | 2020 |
| Sussex Stoves Limited | Construction | 2010 |
| Sussex Thatching Limited | Construction | 2016 |
| Sussex Timber Products Limited | Manufacturing | 1996 |
| Sussex Window Cleaners Ltd | Administrative & support | 2025 |
| Sussex Wizards Ltd | Information & communication | 2017 |
| Sussex Wood Floors Ltd | Construction | 2015 |
| Sussex Zest Limited | Other services | 2015 |
| Sutton Chase Ltd | Wholesale & retail | 2016 |
| SW & STW Limited | Information & communication | 2022 |
| Sweet Lilibet Ltd | Hospitality | 2022 |
| Swift Argent Limited | Professional & scientific | 2009 |
| Swifts Roofing Ltd | Construction | 2024 |
| Swindells & Gentry Company Secretarial Limited | Administrative & support | 2004 |
| Swindells Accounting Limited | Extraterritorial | 2010 |
| Swindells Financial Planning Limited | Financial services | 2004 |
| Swindells LLP | | 2009 |
| Swindells Trustee Services Limited | Extraterritorial | 2015 |
| Sydenham Wines Ltd | Wholesale & retail | 2022 |
| Sykes Cleaning Ltd | Administrative & support | 2019 |
| Sykes Ltd | Administrative & support | 2025 |
| Szekeres Medical Ltd | Health & social care | 2013 |
| T.D. Shaw Limited | Construction | 1972 |
| T.H. Faulkner and Company Limited | Other services | 1961 |
| T4 Management Ltd | Professional & scientific | 2011 |
| TA Homes (Burgess Hill) Limited | Real estate | 2017 |
| TA Homes (Isfield) Limited | Real estate | 2018 |
| Tacklers Limited | Information & communication | 2010 |
| Tagit Limited | Manufacturing | 1997 |
| Tailored Angler Ltd | Wholesale & retail | 2020 |
| Talisman Estates Trading Ltd | Real estate | 2016 |
| Talkom Ltd | Information & communication | 2025 |
| Tanyard Advisory Ltd | Professional & scientific | 2024 |
| Tarak PVT Ltd | Hospitality | 2023 |
| Target Better Ltd | Information & communication | 2012 |
| TAS Underwood Limited | Information & communication | 2015 |
| Tavibon Ltd | Construction | 2025 |
| Taylormade Mortgage Finance Ltd | Financial services | 2013 |
| Taylormade Property Services Limited | Construction | 2013 |
| TBC Electrical Ltd | Construction | 2020 |
| TBS Skin Care Ltd | Wholesale & retail | 2024 |
| TCA Advisory Limited | Professional & scientific | 2026 |
| Team 4 Solutions LLP | | 2011 |
| Team Building With Bite Limited | Professional & scientific | 2024 |
| Team Creative Limited | Professional & scientific | 2003 |
| Technique Kitchens Limited | Construction | 2015 |
| Technotop Limited | Construction | 1986 |
| Techsolved CIC | Information & communication | 2024 |
| Techware Consulting Ltd | Wholesale & retail | 2020 |
| TEH Penguin Mafia B202 Ltd | Real estate | 2025 |
| Temple Grove House Freehold Limited | Households | 2017 |
| TEN 05 Limited | Administrative & support | 2007 |
| Tenth Muse Group Ltd | Information & communication | 2019 |
| Tharros Consulting Ltd | Professional & scientific | 2024 |
| THE Arganist Limited | Wholesale & retail | 2024 |
| THE Coachworks Freehold Company Limited | Households | 2019 |
| THE Coffee House Nutley Limited | Hospitality | 2025 |
| THE Fit Rider Formula Ltd | Education | 2025 |
| THE Flower Shop Buxted Ltd | Wholesale & retail | 2022 |
| THE Formation Creative Consultants International Ltd | Professional & scientific | 2009 |
| THE Gearing Company Ltd | Professional & scientific | 2020 |
| THE Grey Earl Ltd | Hospitality | 2016 |
| THE Grill UCK Ltd | Hospitality | 2025 |
| THE Healthy Head Company Ltd | Professional & scientific | 2019 |
| THE Highlands Nutley Residents Association Limited | Households | 2005 |
| THE Hollies (Snatts Road) Management Limited | Hospitality | 2012 |
| THE Incredible Design Company | Other services | 2002 |
| THE MAC Suite Limited | Wholesale & retail | 2014 |
| THE Marine Connection | Education | 1997 |
| THE Marlows Management Company Limited | Households | 2020 |
| THE Naval and Military Press Holdings Limited | Information & communication | 2014 |
| THE Naval and Military Press Limited | Information & communication | 1992 |
| THE Neuroninjas Community Interest Company | Education | 2026 |