| Sparkles Cleaning (Sussex) Limited | Other services | 2007 |
| Sparks and Ladders Ltd | Construction | 2023 |
| SPC Bookkeeping Limited | Professional & scientific | 2013 |
| Special Educational Facilities Ltd | Education | 2025 |
| Specialist Company Restructure Limited | Professional & scientific | 2021 |
| Spencer Murray Film Services Limited | Administrative & support | 2010 |
| Spice Glory Ltd | Hospitality | 2016 |
| Spicegem Limited | Hospitality | 2025 |
| Spicy Hot Ltd | Extraterritorial | 2020 |
| Spineleigh Limited | Households | 1976 |
| Spinervous Ltd | Health & social care | 2016 |
| Spiritual Fitness Ltd | Other services | 2021 |
| Spooky Arts Ltd | Manufacturing | 2025 |
| SPS Film Lighting Limited | Information & communication | 2016 |
| SPS Lighting Limited | Administrative & support | 1999 |
| Sqknell Ltd | Information & communication | 2023 |
| Squared Industries Limited | Administrative & support | 2025 |
| Squareline Carpentry Ltd | Construction | 2026 |
| ST Business & Consultancy Ltd | Professional & scientific | 2019 |
| ST Francis Park (Haywards Heath) Management Company Limited | Households | 2011 |
| ST George Phoenix Ltd | Real estate | 2007 |
| ST George's - Augustinian Care | Construction | 2003 |
| ST George's Park Limited | Real estate | 2004 |
| ST Luke's Court (Burgess Hill) Residents Association Limited | Households | 1973 |
| ST. Andrew's (Burgess Hill) Pre-School | Education | 2004 |
| ST. Leonard's House Management Limited | Households | 1982 |
| Stafford Foster Limited | Transport & logistics | 2023 |
| Staine Holdings Ltd | Manufacturing | 2015 |
| Stanbury Computer Services Limited | Information & communication | 1995 |
| Star Developments (Sussex) Ltd | Construction | 2019 |
| Star SRI UK Limited | Health & social care | 2010 |
| Stardburste & Co Ltd | Health & social care | 2024 |
| Starlight Residential Care Ltd | Health & social care | 2025 |
| Station Road (Burgess Hill) Freehold Limited | Households | 2017 |
| Stenart Associates Limited | Real estate | 2018 |
| Stephen Palmer Ltd | Health & social care | 2001 |
| Stephens Lighting Services Limited | Other services | 2015 |
| Stepney Commercials Limited | Wholesale & retail | 2013 |
| Steppas Limited | Information & communication | 2020 |
| Stepping Stones Estates Limited | Real estate | 2025 |
| Sterling Financial Wealth Limited | Administrative & support | 2011 |
| STG Travel Limited | Administrative & support | 2015 |
| STH Building Services Ltd | Construction | 2026 |
| Stirling & Johnson Construction Ltd | Construction | 2003 |
| Stirling & Johnson Limited | Construction | 1974 |
| Stock Supply Limited | Wholesale & retail | 2024 |
| Stompbox Strategic Management Ltd | Information & communication | 2024 |
| Stonewell Limited | Construction | 2003 |
| Stoneworks Investments Limited | Financial services | 2019 |
| Stradbroke Island Limited | Construction | 2019 |
| Streeter Properties Ltd | Real estate | 2025 |
| Stuart King Lighting Services Limited | Professional & scientific | 2012 |
| Studio Hardie Limited | Professional & scientific | 2014 |
| Suburban Group Ltd | Construction | 2020 |
| Success Academies Ltd | Education | 2022 |
| Summerfold Place (Burgess Hill) Management Company Limited | Households | 2016 |
| Summers IT Consulting Ltd | Information & communication | 2025 |
| Suni Cleaning Limited | Administrative & support | 2025 |
| Sunshine Cafe (Burgess Hill) Limited | Hospitality | 2019 |
| Supreme Beauty Academy Ltd | Education | 2025 |
| Supreme Beauty and Aesthetics Ltd | Other services | 2021 |
| Supreme Developments Group Ltd | Transport & logistics | 2026 |
| Suresearch Legal Services Limited | Professional & scientific | 2014 |
| Surrey Summer Houses Ltd | Construction | 2025 |
| Sushi Umai Limited | Hospitality | 2025 |
| Sussex & Surrey Partitioning Limited | Construction | 2011 |
| Sussex Active Limited | Health & social care | 2025 |
| Sussex Athletic Performance Academy (Sapa) Ltd | Other services | 2023 |
| Sussex Barbershops Ltd | Other services | 2022 |
| Sussex Chamber of Commerce & Enterprise | Other services | 1990 |
| Sussex Door Company Limited | Construction | 2021 |
| Sussex Drywall Solutions Ltd | Construction | 2011 |
| Sussex Enterprise Limited | Administrative & support | 2001 |
| Sussex Facilities Management Ltd | Construction | 2019 |
| Sussex Fire Doors Ltd | Construction | 2024 |
| Sussex Furniture Painting Ltd | Construction | 2021 |
| Sussex Garden Retreats Ltd | Construction | 2025 |
| Sussex Gate (Haywards Heath) RTM Company Limited | Households | 2013 |
| Sussex Home Checks Ltd | Health & social care | 2020 |
| Sussex Homecare Support Limited | Health & social care | 2016 |
| Sussex Interior Solutions Ltd | Construction | 2025 |
| Sussex Massage Therapy Limited | Other services | 2024 |
| Sussex Media Group Ltd | Information & communication | 2020 |
| Sussex Media Walls Ltd | Construction | 2025 |
| Sussex Metal Fabrications Limited | Manufacturing | 2014 |
| Sussex MOT Centre Limited | Wholesale & retail | 2012 |
| Sussex N S S Karayogam Limited | Other services | 2022 |
| Sussex Osteopathy Limited | Health & social care | 2012 |
| Sussex Real Estate Limited | Real estate | 2020 |
| Sussex Surfacing Limited | Construction | 2011 |
| Sussex Topiary Park Limited | Hospitality | 2020 |
| Sussex Trade Kitchens Ltd | Wholesale & retail | 2019 |
| Sussex Training Ltd | Education | 2018 |
| Sussex Vehicle Services Ltd | Wholesale & retail | 2013 |
| Sussexfoodtrucks Ltd | Hospitality | 2025 |
| Sustainable Home & Garden Ltd | Construction | 2020 |
| Suthamy Ltd | Wholesale & retail | 2025 |
| SW Contractors Limited | Construction | 2025 |
| Sweet Sussex Limited | Manufacturing | 2023 |
| Synapsys Solutions Ltd | Wholesale & retail | 2001 |