| Siriotek Limited | Administrative & support | 2014 |
| Sirius 23 Limited | Arts & recreation | 2018 |
| Sirk Limited | Extraterritorial | 2025 |
| Sirl Limited | Financial services | 2024 |
| Sish Engineering Ltd | Construction | 2019 |
| Site 1 LS Limited | Real estate | 2021 |
| Sitrog Limited | Administrative & support | 2014 |
| Siuyin Optical Limited | Health & social care | 2023 |
| Sivcraft Engineering Limited | Manufacturing | 1987 |
| SIX Five Holdings Limited | Financial services | 2021 |
| SIX Hands LLP | | 2016 |
| Sixti Limited | Professional & scientific | 2012 |
| Sizestorage Ltd | Real estate | 2017 |
| SJ Brighton Ltd | Hospitality | 2026 |
| SJ Collectives Ltd | Professional & scientific | 2025 |
| SJ Harish Ltd | Wholesale & retail | 2022 |
| SJ Legacy Ltd | Other services | 2022 |
| SJ Social Holdings Limited | Financial services | 2022 |
| SJ Social Limited | Information & communication | 2022 |
| SJ Solutions (South East) Ltd | Administrative & support | 2017 |
| SJB Compliance and Validation Limited | Information & communication | 2018 |
| SJB Consultants KL Ltd | Professional & scientific | 2003 |
| SJH Consultancy Ltd | Professional & scientific | 2025 |
| SJK Bookkeeping Services Limited | Professional & scientific | 2005 |
| SJK Installations Ltd | Construction | 2021 |
| SJM Collectables Limited | Wholesale & retail | 2026 |
| SJM Decorating Limited | Construction | 2014 |
| SJM Developments (Southeast) Ltd | Construction | 2019 |
| SJM IM Ltd | Other services | 2023 |
| SJR Management Limited | Professional & scientific | 2025 |
| SJW Transporting Ltd | Administrative & support | 2019 |
| SK Blossoms Limited | Health & social care | 2025 |
| SK Creative Ltd | Information & communication | 2024 |
| SK-12 Limited | Administrative & support | 2020 |
| Skee Ventures Limited | Extraterritorial | 2022 |
| Skeyne Drive Management Co.Limited | Extraterritorial | 1965 |
| Skin LAB Ltd | Other services | 2025 |
| Skinb Ltd | Other services | 2019 |
| Skinilean Limited | Manufacturing | 2013 |
| Skinnygskicks Ltd | Extraterritorial | 2022 |
| SKM Software Support Limited | Information & communication | 2002 |
| Skrda Limited | Real estate | 2023 |
| Sky Traveller Studios Ltd | Information & communication | 2026 |
| Skyborne Ltd | Manufacturing | 2014 |
| Skydeskworks Ltd | Information & communication | 2026 |
| Skylar Nails Worthing Ltd | Other services | 2025 |
| Skyline Bradford Limited | Construction | 2018 |
| Skyline GBS RTM Company Ltd | Households | 2025 |
| Skynexus Limited | Information & communication | 2026 |
| Skyrodd Engineering Ltd | Manufacturing | 2026 |
| Skywalker IT Limited | Construction | 2017 |
| SL Vehicle Sales Limited | Wholesale & retail | 2011 |
| Slabson Ltd | Arts & recreation | 2025 |
| SLC Registrars Limited | Administrative & support | 1982 |
| SLG Financial Solutions Limited | Financial services | 2006 |
| SLG Property Limited | Real estate | 2017 |
| Slicc Ltd | Hospitality | 2023 |
| Slightspace Limited | Administrative & support | 2005 |
| Slimak Ltd | Wholesale & retail | 2021 |
| Sliqnet Ltd | Information & communication | 2011 |
| Slmtt Holdings Limited | Financial services | 2023 |
| Slmtt Limited | Information & communication | 2019 |
| Slowroll Media Ltd. | Information & communication | 2024 |
| Slowtalkinjimmy Ltd | Arts & recreation | 2014 |
| SLT4ME Ltd | Education | 2021 |
| SLZ Limited | Professional & scientific | 2009 |
| SM Carpentry and Building Southeast Ltd | Construction | 2023 |
| SM Davies Limited | Health & social care | 2025 |
| Smac Europe Limited | Manufacturing | 1996 |
| Smalley & Hales Architects Limited | Professional & scientific | 2014 |
| Smallworth Printers Limited | Manufacturing | 1961 |
| Smart Accountancy & Taxation Limited | Professional & scientific | 2006 |
| Smart Accountants (Surrey) Limited | Professional & scientific | 2022 |
| Smart Accountants (Sussex) Limited | Professional & scientific | 2022 |
| Smart Brick Limited | Real estate | 2016 |
| Smart Drive (UK) Driving Tuition Limited | Education | 2010 |
| Smart Flooring Solutions Limited | Construction | 2016 |
| Smart Nutrition Limited | Other services | 2002 |
| Smart Performance (UK) Limited | Arts & recreation | 2013 |
| Smart Property Solutions (Sussex) Ltd | Real estate | 2016 |
| Smart Tuna Limited | Information & communication | 2003 |
| Smart Water Networks Forum | Other services | 2010 |
| Smartdrones Ltd | Professional & scientific | 2024 |
| Smarter-Net Limited | Professional & scientific | 2021 |
| Smartestenergy Business Limited | Energy | 2008 |
| Smartie Pants Limited | Professional & scientific | 2011 |
| Smartpaint Limited | Real estate | 2003 |
| Smash'D Worthing Limited | Hospitality | 2025 |
| Smashover Limited | Hospitality | 2025 |
| SMB Social Work Consulting Limited | Health & social care | 2015 |
| SMC Technical Consultants Limited | Information & communication | 2014 |
| Smdf Holdings Limited | Financial services | 2025 |
| SME Advisor Ltd | Professional & scientific | 2011 |
| Smile Cars Limited | Wholesale & retail | 1999 |
| Smiley's Cafe Ltd | Hospitality | 2019 |
| Smisby Court Limited | Households | 2006 |
| Smithson Recruitment Services Ltd | Administrative & support | 2026 |
| SMJ Landscaping and Building Ltd | Construction | 2023 |
| Smock Alley Limited | Construction | 2020 |
| Smokey’S Kitchen Ltd | Hospitality | 2020 |