| Sebden Steel Service Centres Limited | Wholesale & retail | 1990 |
| Second Ride Ltd | Wholesale & retail | 2026 |
| Secotech Limited | Professional & scientific | 2017 |
| Section One Limited | Professional & scientific | 2025 |
| Sectorhaven Residents Management Limited | Households | 1987 |
| Secuencia Casa Limited | Construction | 2012 |
| Secuencia Limited | Administrative & support | 2008 |
| Secure Archive Solutions Limited | Administrative & support | 2005 |
| Secure Data Limited | Information & communication | 2021 |
| Secure Logic Ltd | Professional & scientific | 2024 |
| Secureiam Limited | Information & communication | 2023 |
| Securepoint Ltd | Information & communication | 2024 |
| Seed Financial Limited | Professional & scientific | 2019 |
| Seeding the Change C.I.C. | Health & social care | 2022 |
| Seeover Limited | Professional & scientific | 2010 |
| Seepup Limited | Public administration | 2023 |
| Sefo Limited | Professional & scientific | 2020 |
| Sefton Street Fraser Homes Limited | Construction | 2022 |
| SEG1 DS Ltd | Information & communication | 2017 |
| Segment One Group Ltd | Professional & scientific | 2018 |
| Segor Limited | Health & social care | 2024 |
| Seguro CAP Ltd | Hospitality | 2019 |
| Selbourne Group Limited | Real estate | 1998 |
| Selbourne Group Services Limited | Hospitality | 2022 |
| Selbourne Properties Limited | Real estate | 1998 |
| Select Motor Trading Limited | Wholesale & retail | 2008 |
| Selemetrics Limited | Administrative & support | 2010 |
| Self Catering Travel Ltd | Extraterritorial | 2011 |
| Sellier Associates Limited | Information & communication | 2024 |
| Selwyns Travel Group Ltd | Transport & logistics | 2020 |
| SEN Casework Services Limited | Professional & scientific | 2021 |
| Senaryo Services Limited | Professional & scientific | 2019 |
| Senoni Limited | Professional & scientific | 2021 |
| Sensible Biotechnologies Limited | Professional & scientific | 2023 |
| Sensible Strategy Limited | Hospitality | 2023 |
| Sensnest Ltd | Professional & scientific | 2025 |
| Sensona Limited | Manufacturing | 2011 |
| Sensornet Limited | Manufacturing | 1997 |
| Sensory Housing Limited | Health & social care | 2021 |
| Sentinel 1 Ltd | Administrative & support | 2019 |
| Sentraconnect Ltd | Wholesale & retail | 2025 |
| Sephton & Sephton Limited | Health & social care | 2016 |
| Sephton Properties Ltd | Real estate | 2024 |
| Sequence 808 Ltd | Professional & scientific | 2024 |
| Sequoia Capital Europe LLP | | 2021 |
| Sequre Investments Ltd | Real estate | 2012 |
| Seren Steel (Midlands) Limited | Professional & scientific | 1987 |
| Seren Steel (South Wales) Limited | Professional & scientific | 1977 |
| Serenity Kitchens Ltd | Wholesale & retail | 2018 |
| Serenity Private Homes Ltd | Real estate | 2021 |
| Serman Consultancy Limited | Information & communication | 2002 |
| Sertiwood Ltd | Transport & logistics | 2023 |
| Servewise Ltd | Professional & scientific | 2025 |
| Service Never Sleeps Limited | Information & communication | 2023 |
| Setoria Security Ltd | Financial services | 2025 |
| Setter Acquisition Limited | Financial services | 2020 |
| Seveer Films Limited | Professional & scientific | 2011 |
| Seveer Media Limited | Information & communication | 2005 |
| Seven Rivers Consulting Limited | Professional & scientific | 2017 |
| Sevenways (Car Parts) Limited | Real estate | 1966 |
| SF Racing Limited | Wholesale & retail | 2023 |
| SFI Global Ltd | Professional & scientific | 2018 |
| Sfpf Ltd | Real estate | 2014 |
| SFZ Healthcare Ltd | Health & social care | 2016 |
| Sgac Holdings Group Limited | Financial services | 2026 |
| SGC Starlight Capital Group LLP | | 2018 |
| SGL 1 Ltd | Real estate | 2020 |
| SGL 12 Ltd | Real estate | 2025 |
| SGL 13 Ltd | Real estate | 2025 |
| SGL 2 Ltd | Real estate | 2020 |
| SGL 3 Ltd | Real estate | 2021 |
| SGL 4 Ltd | Real estate | 2023 |
| SGL 5 Ltd | Real estate | 2023 |
| SGL 6 Ltd | Real estate | 2024 |
| SGL 8 Ltd | Real estate | 2024 |
| SGL 9 Ltd | Real estate | 2024 |
| SGL Carbon Limited | Manufacturing | 1963 |
| Sgmm Limited | Professional & scientific | 2023 |
| SH Biopharma Consult Limited | Administrative & support | 2018 |
| SH Rahman Limited | Professional & scientific | 2020 |
| Shaba Digital Limited | Professional & scientific | 2026 |
| Shabib Advisory Ltd | Financial services | 2018 |
| Shahbaz DR Limited | Health & social care | 2019 |
| Shahi & Company Ltd | Health & social care | 2022 |
| Shahram Radmard Ltd | Health & social care | 2025 |
| Shaizhub Limited | Wholesale & retail | 2025 |
| Shakespeare Street Ltd | Real estate | 2012 |
| Shakil Qureshi Ltd | Health & social care | 2011 |
| Shakti Synergy Limited | Professional & scientific | 2026 |
| Sham Transport Solution Ltd | Transport & logistics | 2020 |
| Shama T/A Luigis Little Italy Ltd | Hospitality | 2024 |
| Shanks Group Ltd | Financial services | 2026 |
| Shaped Spmu Ltd | Other services | 2025 |
| Shaqs Motors Limited | Wholesale & retail | 2024 |
| Share Your Story UK Ltd | Wholesale & retail | 2011 |
| Sharerate Property Management Limited | Households | 1989 |
| Shareshare Limited | Professional & scientific | 2010 |
| Sharks Holdings Limited | Professional & scientific | 2016 |
| Sharp Recovery Group Ltd | Transport & logistics | 2025 |
| Sharpe Intuition Ltd | Professional & scientific | 2012 |