| Scammell's Garage Limited | Wholesale & retail | 2002 |
| Scissors Hair Limited | Other services | 2002 |
| Scott & Sargeant (Properties) Limited | Real estate | 2000 |
| Scott & Sargeant Holdings Limited | Professional & scientific | 1999 |
| Scott and Sargeant Wood Working Machinery Limited | Wholesale & retail | 1989 |
| Scott Military Services Limited | Arts & recreation | 1990 |
| Scrs Limited | Professional & scientific | 2004 |
| SCS Roofing Services Limited | Construction | 2002 |
| Seabright Worthing Limited | Households | 1986 |
| Seaford Digital Designs Limited | Administrative & support | 2001 |
| Seagrave Landscapes Ltd | Construction | 2007 |
| Seal Hotel Development Limited | Real estate | 1991 |
| Seams Building Services Limited | Construction | 2005 |
| Searchway Associates Limited | Professional & scientific | 1998 |
| Seaward Commercial Limited | Real estate | 2007 |
| Seaward Media Limited | Information & communication | 2005 |
| Seaward Properties Limited | Construction | 1991 |
| Seetas Ltd | Construction | 2006 |
| Seldens Mews Limited | Households | 1992 |
| Select Windows and Conservatories Limited | Wholesale & retail | 2006 |
| Selsey Country Club Limited | Arts & recreation | 1957 |
| Selsey Shellfish Direct Ltd | Manufacturing | 2006 |
| Seymour & Curd Limited | Wholesale & retail | 2007 |
| SH Food Sussex Ltd | Hospitality | 2019 |
| Shahera Property Ltd | Real estate | 2025 |
| Shaws Glass Limited | Manufacturing | 1990 |
| Shoreham Car Auctions Limited | Wholesale & retail | 2000 |
| Shoreham House Residents Association Limited | Extraterritorial | 1997 |
| Shoreham Physiotherapy Clinic Limited | Health & social care | 2003 |
| Signature Investments Limited | Real estate | 1998 |
| Simon Fenton Creative Limited | Professional & scientific | 2002 |
| Simpson Electrical Solutions Ltd | Construction | 1959 |
| Sirius Instrumentation Limited | Professional & scientific | 2007 |
| SIX and Seven Chesswood Close (Residents) Company Limited | Households | 2002 |
| Siya Sadan Ltd | Real estate | 2025 |
| SJK Property Management Limited | Households | 2003 |
| SL2 Signs & Graphics Limited | Manufacturing | 2001 |
| Slippery Solutions Limited | Information & communication | 2003 |
| Smith's Heating & Plumbing Services Limited | Construction | 2000 |
| Smsw Services Ltd | Health & social care | 2022 |
| So-Real Records Limited | Professional & scientific | 2000 |
| Software & Sail Design Limited | Information & communication | 1995 |
| Solana Systems Ltd | Information & communication | 2012 |
| Solbrokers Property Agency Limited | Real estate | 2003 |
| Solid Access Scaffolding Ltd | Construction | 2023 |
| Somnowell Ltd | Other services | 2004 |
| Soul DE Diamante Ltd | Wholesale & retail | 2025 |
| Sound Judgement U.K. Limited | Administrative & support | 2007 |
| South by East Property Investments Ltd | Construction | 1992 |
| South Coast Air Conditioning Services Limited | Extraterritorial | 2004 |
| South Coast Evaluation Services Limited | Professional & scientific | 2007 |
| South Coast Refrigeration Services Limited | Manufacturing | 1997 |
| South Coast Software Limited | Information & communication | 1987 |
| South Downs Media Limited | Administrative & support | 2006 |
| South East Legal Systems Limited | | 1986 |
| Southdown Construction Limited | Wholesale & retail | 2008 |
| Southdown Services Limited | Professional & scientific | 2004 |
| Southern Brick Ltd | Wholesale & retail | 2025 |
| Southern Counties Carpet Cleaning Company Limited | Professional & scientific | 1997 |
| Southern Counties Construction Ltd | Wholesale & retail | 2006 |
| Southfarm Plumbing & Heating Limited | Construction | 2005 |
| Southlea (Haywards Heath) Limited | Households | 1974 |
| Space Unit Ltd | Real estate | 2013 |
| Specs of Brighton Limited | Wholesale & retail | 2004 |
| Spect Fairs Ltd | Hospitality | 2026 |
| Spectrum Business Services Limited | Administrative & support | 1994 |
| SPG Exhibitions Limited | Administrative & support | 1993 |
| Springfields Properties Limited | Real estate | 2021 |
| SR Management Services Limited | Financial services | 1999 |
| SRW Investments Limited | Wholesale & retail | 1989 |
| SSJ Limited | Wholesale & retail | 2000 |
| ST Martins Property Asset Management Ltd | Real estate | 2020 |
| ST. George Technology Limited | Manufacturing | 1995 |
| St.Pancras Engineering Works Limited | Real estate | 1946 |
| Stage Flight Limited | Professional & scientific | 2000 |
| Stavemead Limited | Administrative & support | 1985 |
| Stephen Bromley Associates Ltd | Professional & scientific | 2006 |
| Stereopsis Limited | Health & social care | 2000 |
| Stevens SON & Pope LLP | | 2021 |
| Stinton Jones Consulting Engineers LLP | | 2007 |
| Storage Land Limited | Other services | 2004 |
| Storrington Company Services Limited | Professional & scientific | 2004 |
| Storrington Industries Limited | Professional & scientific | 2005 |
| Strange Garden Management Co. Limited | Households | 1961 |
| Stride Innovations Limited | Information & communication | 2017 |
| Stuart Computer Systems Limited | | 1984 |
| Stuart Salisbury Limited | Financial services | 2006 |
| Sturdy Edwards (Financial Services) Limited | Financial services | 1999 |
| Sturdy Edwards (Insurance Brokers) Limited | Financial services | 1999 |
| Sturdy Edwards Holdings Limited | Financial services | 2005 |
| Stylehurst Farm Management Company Limited | Households | 2002 |
| Suchnoon Limited | Agriculture & fishing | 1981 |
| Suite Spot Ventures Ltd | Administrative & support | 2021 |
| Sumar Properties Limited | Real estate | 1963 |
| Survey Publisher Ltd. | Information & communication | 2000 |
| Sussex Campervans EOT Limited | Administrative & support | 2024 |
| Sussex Chiro Limited | Health & social care | 2003 |
| Sussex Coastal Homes Limited | Real estate | 2004 |
| Sussex Goldsmiths Limited | Wholesale & retail | 2004 |
| Sussex Kitchen Designs Ltd | Wholesale & retail | 2007 |