| South East Marquees Ltd | Administrative & support | 2020 |
| South Point Serviced Offices LLP | | 2015 |
| Southdown Place (Ardingly) Management Ltd | Administrative & support | 2019 |
| Southern Counties Air Conditioning Limited | Construction | 2014 |
| Southern Site Services Limited | Construction | 2017 |
| Southern Testing Laboratories Limited | Professional & scientific | 1987 |
| Southview Accounting Limited | Professional & scientific | 2018 |
| Southwick House Management Limited | Households | 1986 |
| Spa Tech Solutions Limited | Information & communication | 2025 |
| Spaceium Technologies Ltd | Manufacturing | 2021 |
| Sparkle Carpet Cleaning East Grinstead Ltd | Administrative & support | 2023 |
| Spartaclaim Limited | Transport & logistics | 1985 |
| Specialist Sourcing Limited | Wholesale & retail | 2019 |
| Spectrum Painting & Decorating Limited | Construction | 2002 |
| Speech UP Ltd | Education | 2011 |
| Speed of Light Productions Limited | Information & communication | 2002 |
| Spells by MIA Ltd | Wholesale & retail | 2025 |
| SPF Aviation Ltd | Professional & scientific | 2023 |
| SPH Holdings Limited | Financial services | 2024 |
| Spice Platform Limited | Hospitality | 2019 |
| Spires Hairdressing (Copthorne) Limited | Other services | 2013 |
| Spires Hairdressing (East Grinstead) Limited | Other services | 2013 |
| Spirit, Mind & Body Limited | Other services | 2022 |
| Spring Dragon Ltd | Hospitality | 2018 |
| Springvale M&M Limited | Agriculture & fishing | 2024 |
| Spruce Place Management Co. Ltd. | Households | 2006 |
| Square PEG Innovations Ltd | Wholesale & retail | 2022 |
| Srcc Professional Services (UK) Ltd | Administrative & support | 2024 |
| SRG Capital Group Ltd | Financial services | 2025 |
| SRT Tax Consulting Limited | Professional & scientific | 2017 |
| SS Residential PVT Limited | Real estate | 2025 |
| Ssdia Ltd | Financial services | 2022 |
| ST Consult Ltd | Construction | 2012 |
| ST Faiths Clinic Limited | Health & social care | 2015 |
| ST James Mews Limited | Households | 2010 |
| ST. Bede's Place Management Co Ltd | Households | 2025 |
| Stable Locums Ltd | Administrative & support | 2020 |
| Stacy Shoots Brands Ltd | Professional & scientific | 2025 |
| Stag Consulting Limited | Professional & scientific | 2024 |
| Stainless Steel Fixings Limited | Manufacturing | 1984 |
| Standard Electrical Services Ltd | Construction | 2022 |
| Stanford Grey Ltd | Real estate | 2016 |
| Stansted Ventures Ltd | Arts & recreation | 2016 |
| Star Barbers East Grinstead Limited | Other services | 2022 |
| Star High Goals Ltd | Education | 2024 |
| Starbap International Limited | Construction | 2009 |
| Start to Finish Music Ltd | Arts & recreation | 2021 |
| State Safety Global Limited | Professional & scientific | 2016 |
| Staycated Ltd | Real estate | 2025 |
| Steall Solutions Ltd | Professional & scientific | 2022 |
| Steam Boiler Hire UK Ltd | Construction | 2024 |
| Step Ahead Social Enterprise Community Interest Company | Administrative & support | 2008 |
| Stephen Parker Associates Limited | Administrative & support | 1999 |
| Stephens AV & Security Ltd | Administrative & support | 2026 |
| Sterling International (UK) Limited | Wholesale & retail | 2013 |
| Sterling VIP Limited | Other services | 2023 |
| Steven Boorer Consulting Limited | Administrative & support | 2003 |
| Stewart Cambridge Limited | Information & communication | 2007 |
| Stil Lifestyle (Forest ROW) Ltd | Wholesale & retail | 2021 |
| Still Human Music Ltd | Information & communication | 2013 |
| Stjb Advisory Limited | Professional & scientific | 2015 |
| STL (Holdings) Limited | Professional & scientific | 1999 |
| Stock Taking Services (BOB Mita) Ltd. | Administrative & support | 2010 |
| Stockbridge Properties Limited | Real estate | 2016 |
| Stockbridge Sussex Limited | Real estate | 2012 |
| Stokeswood Construction Limited | Administrative & support | 2017 |
| Stone and Baxter Homes Limited | Real estate | 2018 |
| Stone's Family Butchers Ltd | Wholesale & retail | 2018 |
| Stonelands Residents Association Limited | Households | 1997 |
| Stophers Racing Kennels Ltd | Arts & recreation | 2015 |
| Stream Park Residents Association Ltd | Households | 2022 |
| Streamline Production Ltd | Construction | 1999 |
| Strivenn Limited | Professional & scientific | 2019 |
| Strng Than Cherry Ltd | Wholesale & retail | 2025 |
| Studio 859 Ltd | Administrative & support | 2023 |
| Studio Bailen Ltd | Information & communication | 2021 |
| Studio Mille Ltd | Information & communication | 2024 |
| Stuhead Limited | Information & communication | 2018 |
| Style Insurance and Mortgage Services Limited | Financial services | 2009 |
| Suburban Bottlestore Limited | Wholesale & retail | 2021 |
| Success Orientation Ltd | Wholesale & retail | 2019 |
| Sun&Dong Estate Investment Limited | Real estate | 2024 |
| Sunderland & Co Group Ltd | Wholesale & retail | 2026 |
| Sunnyside Close Management Company Limited | Households | 2021 |
| Sunshine Park Ltd | Manufacturing | 2024 |
| Superior Decorating Limited | Other services | 2005 |
| Superior Decorating Supplies Ltd | Wholesale & retail | 2025 |
| Superiorbath Repair Ltd | Administrative & support | 2017 |
| Supernova Sales Co. Limited | Wholesale & retail | 2025 |
| SUPPLIES4HEAT Limited | Wholesale & retail | 2009 |
| Supreme Pharmatech United Kingdom Ltd | Households | 2019 |
| Supremely Ltd | Administrative & support | 2015 |
| Surrey Cost & Project Management Limited | Professional & scientific | 2017 |
| Surrey Mower Mechanic Limited | Manufacturing | 2026 |
| Surrey Pool Services Limited | Administrative & support | 2007 |
| Surveygoo Limited | Professional & scientific | 2010 |
| Sussex Auto Works Ltd | Wholesale & retail | 2020 |
| Sussex Classics Ltd | Wholesale & retail | 2011 |
| Sussex Curry Kitchen Ltd | Hospitality | 2024 |
| Sussex Door to Door Distribution Ltd | Professional & scientific | 2018 |