| Safe Site Group Ltd | Administrative & support | 2021 |
| Safe Site Security Solutions Limited | Administrative & support | 2015 |
| Safesite (GB) Ltd | Administrative & support | 2011 |
| Salestone Ltd | Manufacturing | 2020 |
| Salisbury Site LLP | | 2005 |
| Salmar Limited | Professional & scientific | 2014 |
| Salon in the Square (Angmering) Ltd | Other services | 2023 |
| Salt Earth Limited | Construction | 2016 |
| Salter Properties Limited | Real estate | 1962 |
| Samadhi Therapy Limited | Administrative & support | 2008 |
| Samlogic Ltd. | Information & communication | 2010 |
| Santhomonline Limited | Wholesale & retail | 2023 |
| SAR Properties (UK) Limited | Professional & scientific | 2002 |
| Satellite Consumer Services Limited | Manufacturing | 2006 |
| Satellite Customer Care Limited | Financial services | 2007 |
| Saunders Specialised Services Limited | Manufacturing | 1973 |
| Saxon Reach (NO. 1) Management Limited | Households | 1997 |
| Saxon Reach (NO.2) Management Limited | Households | 1997 |
| SAY IT Loud Marketing Limited | Administrative & support | 2001 |
| SB Cars Sussex Ltd | Wholesale & retail | 2025 |
| SC Homes Sussex Ltd | Real estate | 2025 |
| SCC Enterprise Limited | Health & social care | 2016 |
| Schlich Limited | Administrative & support | 2004 |
| Schoolsworks Academy Trust | Education | 2012 |
| Scorpio Property Limited | Construction | 2000 |
| Scott Morley Plumbing Ltd | Construction | 2022 |
| Scott's Landscapes & Clearances Limited | Administrative & support | 2022 |
| Scoville Purchasing Ltd | Professional & scientific | 2025 |
| Scrub and Tumble Launderette Ltd | Other services | 2023 |
| SCS Site Installations Ltd | Construction | 2000 |
| SCW Automotive Limited | Wholesale & retail | 2019 |
| SCW Electrical Solutions Ltd | Construction | 2019 |
| SDP Recruitment Limited | Administrative & support | 2024 |
| Sea Estate Residents Association Limited | Other services | 2004 |
| Sea Scope Ltd | Real estate | 2019 |
| Seacroft Estate Management Limited | Households | 2006 |
| Seahorse Marine School Limited | Education | 2023 |
| Seal Events Limited | Professional & scientific | 2004 |
| Seascapes Freehold Limited | Administrative & support | 2009 |
| Seaspray Residents' Association Limited | Households | 1984 |
| SEC Classics Ltd | Wholesale & retail | 2024 |
| Seckloe 267 Limited | Professional & scientific | 2005 |
| Seed Psychology Limited | Health & social care | 2016 |
| Seen, Heard, Empowered Ltd | Health & social care | 2023 |
| Self Storage Containers Sussex Ltd | Extraterritorial | 2026 |
| Self Storage Space (Trading) Limited | Real estate | 1975 |
| Selsey Court (Management) Limited | Households | 1982 |
| Serui Source Limited | Health & social care | 2003 |
| Servac Limited | Other services | 2006 |
| Servac Trains Limited | Professional & scientific | 2006 |
| Severne Snow Limited | Professional & scientific | 2002 |
| Sexton Holdings Limited | Construction | 2002 |
| SGJ Wellness Ltd | Health & social care | 2020 |
| Shaftesbury Court (Rustington) Limited | Households | 1975 |
| Shandhill Limited | Real estate | 1988 |
| Shane Spence Design Ltd | Professional & scientific | 2020 |
| Shanklin Court Hove RTM Company Limited | Households | 2009 |
| Sharepoint Tech Limited | Information & communication | 2016 |
| Sharpak Group Holding Ltd | Professional & scientific | 2011 |
| Sharpak Healthcare Ltd | Manufacturing | 2024 |
| Sheep Lane Management Limited | Real estate | 2024 |
| Sheys Electrical Solutions Limited | Construction | 2020 |
| Shina Ltd | Education | 2022 |
| Shine on Commercial Cleaning Ltd | Administrative & support | 2022 |
| Shine on Ltd | Administrative & support | 2020 |
| Shoreline (UK) Limited | Wholesale & retail | 2002 |
| Shoreline Management Holdings Ltd | Other services | 2026 |
| Shs(Shaw Holistic Solutions) Ltd | Manufacturing | 2023 |
| Sian Lewis Limited | Professional & scientific | 2014 |
| Sideline PA Ltd | Administrative & support | 2025 |
| Sigma Products Limited | Manufacturing | 1995 |
| Sigrun Customs Limited | Wholesale & retail | 2022 |
| Silco Products Limited | Manufacturing | 2011 |
| Silpro Ltd. | Manufacturing | 1996 |
| Silver City Takaway Limited | Hospitality | 2024 |
| Silveredge Properties Limited | Construction | 2022 |
| Silvervale Ltd | Wholesale & retail | 2020 |
| Simbiotix Ltd | Professional & scientific | 2018 |
| Simon Woodhead Limited | Professional & scientific | 2019 |
| Simply CJ Ltd | Wholesale & retail | 2017 |
| Simpson Electrical Holdings Ltd | Financial services | 2025 |
| Sinclair White & Co Limited | Professional & scientific | 2015 |
| SJ Peace Ltd | Construction | 2019 |
| SJH Property Investments Ltd | Real estate | 2018 |
| SK Ocular Aesthetics Ltd | Health & social care | 2021 |
| Skandi HUS & HEM Ltd | Real estate | 2021 |
| Skin and Bony Ltd | Arts & recreation | 2018 |
| SKR Electrical Limited | Construction | 2011 |
| Slam Dunk Digital Limited | Professional & scientific | 2016 |
| Slate Properties Limited | Real estate | 2017 |
| Smart Host Services Limited | Information & communication | 2013 |
| Smartfact Ltd | Professional & scientific | 2024 |
| Smith FS Ltd | Financial services | 2023 |
| Smith Heating Ltd | Construction | 2026 |
| Smith Sedgewick Consulting LLP | | 2012 |
| SMJ Roofing and Building Ltd | Construction | 2023 |
| Smoke Puppy Ltd | Information & communication | 2024 |
| Smoke Signals 25 Limited | Hospitality | 2025 |
| Smoking Hogs Ltd | Hospitality | 2024 |
| Snowkite Limited | Professional & scientific | 2012 |