| Scout Impact Ltd | Professional & scientific | 2017 |
| Scriptor Ltd | Information & communication | 2023 |
| Scripts ETC Ltd | Arts & recreation | 2013 |
| Scruffy Store Ltd | Wholesale & retail | 2023 |
| Scrumingit Ltd | Information & communication | 2024 |
| SCS Construction Sussex Ltd | Construction | 2025 |
| Sculpted by Kamila Ltd | Other services | 2021 |
| SD Cc&C Services Ltd | Professional & scientific | 2021 |
| SD Eastworth House Limited | Real estate | 2020 |
| SD Properties (UK) Limited | Construction | 2013 |
| SDB Land Limited | Construction | 2014 |
| SDT MNN Limited | Real estate | 2024 |
| SE Exclusive Ltd | Arts & recreation | 2024 |
| SE Group Limited | Financial services | 2025 |
| Sea Breeze Hove Ltd | Hospitality | 2025 |
| Sea-Charter Properties Limited | Construction | 1963 |
| Seacliffe (1959) Limited | Households | 1959 |
| Seacoft Ltd | Information & communication | 2026 |
| Seadragon Backpackers Limited | Hospitality | 2007 |
| Seafield Properties (Hove) Limited | Households | 1960 |
| Seafield SOL Limited | Households | 2012 |
| Seafields Limited | Financial services | 1995 |
| Seaford and District Motor Services Limited | Transport & logistics | 2015 |
| Seaford Consulting Limited | Professional & scientific | 2026 |
| Seaford Scene Limited | Information & communication | 2024 |
| Seafront Hospitality Ltd | Hospitality | 2022 |
| Seagullsfishandchips Limited | Hospitality | 2019 |
| Seahaven Housing Limited | Real estate | 2025 |
| Searchtribes Ltd | Administrative & support | 2010 |
| Seasda Limited | Wholesale & retail | 2025 |
| Seaside Eastbourne Ltd | Real estate | 2018 |
| Seaside Events Limited | Arts & recreation | 2023 |
| Season and BEE Ltd | Education | 2015 |
| Seaview Property Investments Limited | Real estate | 2020 |
| Seb-Services Cleaning Ltd | Administrative & support | 2020 |
| Second Avenue Interiors Ltd | Construction | 2024 |
| Second Best Ltd | Wholesale & retail | 2023 |
| Second Nature Landscapes Limited | Administrative & support | 2007 |
| Secrets Worth Sharing CIC | Other services | 2024 |
| Securafirm Ltd | Information & communication | 2023 |
| Secure Connect Technology Limited | Information & communication | 2019 |
| Security Assured Limited | Construction | 2017 |
| Seden Durmaz Limited | Manufacturing | 2015 |
| Seek Limited | Information & communication | 1998 |
| Seen PR Ltd | Professional & scientific | 2004 |
| Seentalentmgt Ltd | Administrative & support | 2024 |
| Sel-A-Dore Ltd. | Wholesale & retail | 2008 |
| Selborne Court Limited | Households | 1996 |
| Selborne House Management Company Limited | Households | 2000 |
| Selborne Place Limited | Real estate | 2006 |
| Selborne Solutions Limited | Education | 2025 |
| Selden Arms Ltd | Hospitality | 2023 |
| Select Premier Limited | Wholesale & retail | 2012 |
| Selective Property Management Limited | Real estate | 2015 |
| Selectus Luxury Circle Ltd | Wholesale & retail | 2025 |
| Selfiebook Ltd | Information & communication | 2020 |
| Selin Eastbourne Ltd | Other services | 2016 |
| Selko (SE) Limited | Professional & scientific | 1987 |
| Sell on Site Ltd | Information & communication | 2011 |
| Sell Well Ltd | Construction | 2025 |
| Sellindge Solar Limited | Energy | 2013 |
| Sellox Limited | Administrative & support | 2016 |
| Semesta Holland Limited | Real estate | 1999 |
| Semiofest Ltd | Information & communication | 2013 |
| Semveta Ltd | Wholesale & retail | 2020 |
| SEN Taxi Ltd | Transport & logistics | 2026 |
| Senator Building & Maintenance Limited | Construction | 2022 |
| Seneca Services Ltd | Construction | 2021 |
| Seniors Helping Seniors in Brighton and Hove Limited | Health & social care | 2026 |
| Senqu Consult Ltd | Professional & scientific | 2021 |
| Sensong Workshops CIC | Education | 2025 |
| Sensussex Ltd | Hospitality | 2019 |
| Sentrahive Ltd | Information & communication | 2017 |
| SEO Creative Ltd | Information & communication | 2023 |
| Septua Limited | Real estate | 2018 |
| Seraphic Assist Limited | Professional & scientific | 2019 |
| Serene Brunswick Limited | Households | 1978 |
| Serene Studios Sussex Limited | Arts & recreation | 2026 |
| Serenity Flats Limited | Real estate | 2025 |
| Serve Communications Ltd | Professional & scientific | 2024 |
| Service Box Group Limited | Other services | 2017 |
| Seryt Fleet Limited | Transport & logistics | 2012 |
| Seryt Limited | Wholesale & retail | 2015 |
| SESMP110 Lower House Solar Farm Limited | Energy | 2012 |
| Sessionlord Ltd. | Information & communication | 2014 |
| Seven Dials Limited | Households | 1992 |
| Seven Feathers Hospitality Ltd | Hospitality | 2025 |
| Seven Oriental Place Limited | Households | 1993 |
| Seven Sisters BUS and Coach Company Limited | Transport & logistics | 2018 |
| Seven Sisters Seaford Ltd | Construction | 2022 |
| Seventeen Sackville Road RTM Company Limited | Households | 2017 |
| Seventy Three Degrees Construction Limited | Construction | 2022 |
| Severs Design Limited | Professional & scientific | 2010 |
| SFF Estates Limited | Real estate | 2025 |
| SG Collection Limited | Wholesale & retail | 2026 |
| SG Group & Sons Limited | Wholesale & retail | 2016 |
| SG Joinery Interiors Ltd | Construction | 2014 |
| SG Trade Cars Limited | Wholesale & retail | 2022 |
| SGB Project Management Limited | Information & communication | 2011 |
| SGD2 UK Ltd | Extraterritorial | 2020 |