| Swan Homes Holdings Limited | Real estate | 2023 |
| Swan Homes Limited | Construction | 2003 |
| Swan South Yorkshire Limited | Construction | 2013 |
| Swan Spilsby Limited | Construction | 2022 |
| Swan Street (Bawtry) Limited | Real estate | 2019 |
| Swan Studios Pilates Ltd | Arts & recreation | 2025 |
| Swan Wellington Ltd | Hospitality | 2025 |
| Swanborne Limited | Other services | 2022 |
| Swans Productions Ltd | Arts & recreation | 2020 |
| Swastik Design Limited | Information & communication | 2025 |
| Swazza Ltd | Information & communication | 2017 |
| SWE Consulting Ltd | Professional & scientific | 2016 |
| Sweepe Ltd | Wholesale & retail | 2026 |
| Sweet Apple Property Company Limited | Construction | 2020 |
| Sweet BEE Ltd | Real estate | 2023 |
| Sweetpea Productions Ltd | Professional & scientific | 2016 |
| Sweetrise Ltd | Extraterritorial | 2026 |
| Sweltsje Ltd. | Professional & scientific | 2014 |
| Swift 1524 Limited | Construction | 1986 |
| Swift Cabs Doncaster Ltd | Transport & logistics | 2025 |
| Swift Drift Limited | Transport & logistics | 2025 |
| Swift Exhibitions Ltd | Construction | 2013 |
| Swift Heating & GAS Services Ltd | Construction | 2018 |
| Swift Hire Group Ltd | Other services | 2024 |
| Swift Link Logistics Ltd | Transport & logistics | 2024 |
| Swift Orchard Online Ltd | Extraterritorial | 2025 |
| Swift Property Group Management Ltd | Real estate | 2024 |
| Swift Property Group Serviced Accommodation Ltd | Administrative & support | 2025 |
| Swift Shifts School of Motoring LLP | | 2024 |
| Swift Xpress Limited | Transport & logistics | 2026 |
| Swift's Funfairs Limited | Arts & recreation | 2025 |
| Swiftcheck Software Limited | Information & communication | 2013 |
| Swiftfix Aluminium Ltd | Construction | 2014 |
| Swiftline Car Logistics Ltd | Extraterritorial | 2026 |
| Swiftmarketonline Ltd | Wholesale & retail | 2026 |
| Swimplay Ltd | Education | 2021 |
| Swimstars & Dolphins Limited | Arts & recreation | 2009 |
| Swimstars Court Parking Ltd | Real estate | 2024 |
| Swimstars Group Ltd | Financial services | 2024 |
| Swimstars HQ Ltd | Real estate | 2024 |
| Swimstars Lincoln Limited | Arts & recreation | 2024 |
| Swinden House Ltd | Construction | 2023 |
| Swinden Town Houses Ltd | Construction | 2026 |
| Swinmedia Limited | Wholesale & retail | 2023 |
| Swinton Street Studios LLP | | 2015 |
| Swiss Europe Global Ltd | Wholesale & retail | 2024 |
| Switch Lifestyles Ltd | Financial services | 2019 |
| SWM Estates Ltd | Real estate | 2025 |
| Sword Marketing Ltd | Professional & scientific | 2023 |
| SWR Electrical & Security Ltd | Construction | 2014 |
| SY Foilers Limited | Administrative & support | 2011 |
| SY Haulage Limited | Transport & logistics | 2024 |
| SY Quality Carers Ltd | Health & social care | 2024 |
| SY Retail Ltd | Wholesale & retail | 2024 |
| SYB Futsal Ltd | Education | 2023 |
| Sycad Technical Services Limited | Professional & scientific | 2021 |
| Sycon Contracts Limited | Construction | 2015 |
| Sycon Group Limited | Financial services | 2023 |
| Sycon Projects Ltd | Construction | 2019 |
| Sycon Property Management Limited | Real estate | 2023 |
| SYD Engineering Limited | Manufacturing | 2007 |
| SYD Rogers Limited | Construction | 2014 |
| Sydney Hill Property Ltd | Real estate | 2021 |
| Sydney House Wellness Ltd | Arts & recreation | 2023 |
| Syed Traffic Management Ltd | Public administration | 2022 |
| Syenti Holdings Limited | Other services | 2024 |
| Syenti Limited | Wholesale & retail | 2021 |
| Sykes Joinery Limited | Manufacturing | 2022 |
| Sykes Learning and Locum Limited | Wholesale & retail | 2020 |
| Sykes Plumbing & Heating Ltd | Construction | 2018 |
| Sykes Rigging Services Limited | Mining & quarrying | 2014 |
| Sylas Solutions Limited | Administrative & support | 2016 |
| Sylvia and Stella Limited | Professional & scientific | 2019 |
| Symitah Limited | Manufacturing | 2024 |
| Syncgrid Ltd | Information & communication | 2026 |
| Synergies Developments Limited | Real estate | 2018 |
| Synergy Supplements Ltd | Wholesale & retail | 2025 |
| Synergy UK Developments Limited | Construction | 2015 |
| Synergy Wines Limited | Wholesale & retail | 2020 |
| Synergy-Analytica Ltd | Information & communication | 2020 |
| Synetiq Nominees Limited | Wholesale & retail | 2019 |
| Synthax AI Ltd | Information & communication | 2023 |
| Syntrio Networks Ltd | Extraterritorial | 2026 |
| SYR Building Limited | Construction | 2022 |
| SYR Shisha Ltd | Manufacturing | 2023 |
| Syriadar Limited | Information & communication | 2026 |
| Syringa Court (BMC) Ltd | Real estate | 2019 |
| Syringa Court Lettings Ltd | Real estate | 2022 |
| SYS Racing Limited | Arts & recreation | 2025 |
| Sysco Environmental Ltd | Professional & scientific | 2013 |
| Syslom Limited | Information & communication | 2025 |
| Systemsight Limited | Extraterritorial | 2017 |
| Syvc Ltd | Wholesale & retail | 2025 |
| SZ Trading & Services Ltd | Wholesale & retail | 2025 |
| Szasz Bakery & Chimney Cake Ltd | Wholesale & retail | 2025 |
| SZG Services Ltd | Wholesale & retail | 2019 |
| Szybki Denixs Ltd | Transport & logistics | 2023 |
| Szymon-Transport Ltd | Administrative & support | 2026 |
| T & a Corporation Ltd | Administrative & support | 2013 |
| T & C Plane Ltd | Wholesale & retail | 2003 |