| Stamp World Exhibitions | Administrative & support | 1986 |
| Stanmer Tea Rooms Ltd | Hospitality | 2018 |
| Starkey Properties Management LLP | | 2020 |
| Starkings Communications Ltd | Professional & scientific | 2024 |
| Station Yard Kingswood Management Company Limited | Households | 2023 |
| Statutory Computing Ltd | Information & communication | 1996 |
| Steans Properties Limited | Real estate | 2026 |
| Stepet Limited | Health & social care | 2026 |
| Steve Merchant Ltd | Hospitality | 2025 |
| Steven Art Kitchen Limited | Hospitality | 2025 |
| Steves Staycation Ltd | Hospitality | 2023 |
| Stone Cross Auto Repairs and Valeting Ltd | Wholesale & retail | 2021 |
| Stonebeach Property Services Ltd | Real estate | 2025 |
| Storiworks Ltd | Professional & scientific | 2022 |
| Stour Fishing Syndicate Limited | Agriculture & fishing | 2017 |
| Straight UP Trees Ltd | Administrative & support | 2016 |
| Strata OKR Ltd | Professional & scientific | 2021 |
| Stratton Car Company Limited | Wholesale & retail | 2004 |
| Stratton Group of Sussex Ltd | Financial services | 2024 |
| Stratton Motor Services Limited | Wholesale & retail | 2019 |
| Strike Property Limited | Real estate | 2019 |
| Strive AV Holdings Limited | Financial services | 2021 |
| Strive AV Limited | Information & communication | 2000 |
| Strong AS a Lion Ltd | Water & waste | 2022 |
| Stronghold Commercial Limited | Real estate | 2018 |
| Studio 08 Architecture + Planning Limited | Professional & scientific | 2003 |
| Studio Albatross Limited | Arts & recreation | 2017 |
| Studio Bowden Limited | Professional & scientific | 2010 |
| Studio Coryndon Ltd. | Arts & recreation | 2014 |
| Studio LOW Limited | Arts & recreation | 2015 |
| Studio Rackowe Limited | Arts & recreation | 2022 |
| Subtotal Ltd | Construction | 2016 |
| Sudz Laundry Services Ltd | Other services | 2026 |
| Suffolk House Bexhill Limited | Households | 2006 |
| Sugi Ltd | Health & social care | 2022 |
| Sukamde Limited | Health & social care | 2011 |
| Summit Property and Maintenance Ltd | Construction | 2023 |
| Sun Communities UK Parks Ltd | Hospitality | 1992 |
| Sunrise Gourmet (Bexhill) Limited | Hospitality | 2022 |
| Sunshine London Ltd | Other services | 2019 |
| Superior Scaffold Ltd | Construction | 2023 |
| Surveys S.E. Ltd | Construction | 2010 |
| Sussex Beds (Maidstone) Ltd | Wholesale & retail | 2019 |
| Sussex Beds (Tunbridge Wells) Ltd | Wholesale & retail | 2019 |
| Sussex Building Services Limited | Construction | 2022 |
| Sussex Ceramics Limited | Construction | 2011 |
| Sussex Coast Scaffolding Ltd | Construction | 2020 |
| Sussex County Services Ltd | Administrative & support | 2021 |
| Sussex Court (Old Town) Limited | Hospitality | 2001 |
| Sussex EPC & Retrofit Ltd | Administrative & support | 2026 |
| Sussex Events Limited | Arts & recreation | 2012 |
| Sussex Gardens Flat Owners (East Dean) Limited | Households | 1988 |
| Sussex Land Holdings Ltd | Real estate | 2019 |
| Sussex New Homes Ltd | Real estate | 2019 |
| Sussex Piling & Groundworks Ltd | Construction | 2025 |
| Sussex Refurbishments Ltd | Construction | 2010 |
| Sussex Staffing Ltd | Administrative & support | 2015 |
| Sussex Sunrise Real Estates Ltd | Real estate | 2019 |
| Sussex Traders Limited | Wholesale & retail | 2020 |
| Sussex Used Cars Ltd | Wholesale & retail | 2026 |
| Suzi Aplin Limited | Information & communication | 2016 |
| SW1 Consultants Limited | Other services | 2008 |
| Sweet Music Productions Limited | Other services | 2000 |
| Sydenham Court Management Company Limited | Households | 1980 |
| Szabo Curtains Ltd | Wholesale & retail | 2019 |
| Szabo Limited | Wholesale & retail | 2007 |
| T & G Maintenance & Management Limited | Real estate | 2016 |
| T & L Management Ltd. | Transport & logistics | 2002 |
| T&G Building and Development Services Limited | Construction | 2018 |
| T.S Electrical Services (Sussex) Limited | Construction | 2018 |
| Tachbura TTF Ltd | Transport & logistics | 2025 |
| TAG Holdings and Developments Limited | Construction | 2020 |
| TAJ Mahal SA Limited | Hospitality | 2021 |
| Taja-Leen Limited | Real estate | 2001 |
| Talisman Deed Properties Ltd | Real estate | 2015 |
| Tanglewood Coppice Limited | Households | 1971 |
| Tannclan Ltd | Information & communication | 2026 |
| Tapestry at Blackfriars Management Company Limited | Real estate | 2026 |
| Tara Robertson Properties Limited | Real estate | 2016 |
| Tarisa Imaging Ltd | Health & social care | 2026 |
| Tashmi Ltd | Wholesale & retail | 2018 |
| Tate Gardening Services Ltd | Administrative & support | 2026 |
| Tates Estates Ltd | Real estate | 2022 |
| Taylor Automotive Ltd | Wholesale & retail | 2022 |
| TBD Media Ltd | Professional & scientific | 2020 |
| Tbwr Properties Limited | Construction | 2019 |
| TD Nails & Spa Ltd | Other services | 2024 |
| Tea N Coffee Ltd. | Hospitality | 2014 |
| Team Care Healthcare Ltd | Health & social care | 2019 |
| Team Kash Consulting Ltd | Information & communication | 2020 |
| Tech-Fix Vacuum Cleaner Service Limited | Wholesale & retail | 2026 |
| Teddington INK Ltd | Other services | 2024 |
| Teiresian Ltd | Manufacturing | 2023 |
| Tempset Ltd | Health & social care | 2025 |
| Terrapinn Leasing Ltd | Real estate | 2022 |
| Terrapinn Properties Ltd | Real estate | 2018 |
| TF Flooring Limited | Construction | 2017 |
| TF Home Improvements Ltd | Construction | 2024 |
| Thaler Media Ltd | Information & communication | 2026 |
| Thaweewan Ltd | Hospitality | 2017 |