| Swimbrite Swimming School Ltd | Arts & recreation | 2013 |
| Swimsport Retail Limited | Wholesale & retail | 2023 |
| Swincar Nurseries Limited | Wholesale & retail | 2025 |
| Swincar Signature Landscapes Ltd | Administrative & support | 2025 |
| Swine Catering Limited | Hospitality | 2024 |
| Swing Renegades Ltd | Education | 2016 |
| Swingantiswing Limited | Health & social care | 2011 |
| Swinnow Holdings Limited | Financial services | 2023 |
| Swish Tech Limited | Professional & scientific | 2017 |
| Swish Technologies Ltd | Information & communication | 2021 |
| Swishfix Limited | Construction | 2026 |
| Swiss & Co Trading Ltd | Wholesale & retail | 2020 |
| Swiss Bear UK Ltd | Wholesale & retail | 2023 |
| Swiss Haven Ltd | Real estate | 2023 |
| Swiss Haven Management Ltd | Real estate | 2026 |
| Swiss Right Packaging Ltd | Administrative & support | 2026 |
| Swiss Rockets UK Limited | Professional & scientific | 2026 |
| Swissly Limited | Hospitality | 2024 |
| Switalskis Solicitors Limited | Professional & scientific | 2014 |
| Switch Electrical Leeds Limited | Manufacturing | 2023 |
| Switch Energy Network Ltd | Construction | 2019 |
| Switch Power Distribution Ltd. | Construction | 2017 |
| Switch Properties Leeds Ltd | Real estate | 2023 |
| Switch Your Energy Ltd | Professional & scientific | 2016 |
| Switchdye Limited | Manufacturing | 2025 |
| Switching Skips Services Ltd | Water & waste | 2025 |
| Switchsaw Holdings Limited | Financial services | 2021 |
| Switchup Electrics and Home Improvements Ltd | Construction | 2023 |
| Swithens Farm Livery Yard Limited | Arts & recreation | 2011 |
| Swithens Mews Management Company Ltd | Real estate | 2011 |
| Swithlove Ltd | Wholesale & retail | 2024 |
| SWJ Electrical Ltd | Construction | 2024 |
| Swoop Africa Limited | Financial services | 2025 |
| Swoop Services Ltd | Administrative & support | 2025 |
| Sword of Spirit Distillery Limited | Manufacturing | 2013 |
| SWQ Property Ltd | Real estate | 2021 |
| SWQ Security Ltd | Administrative & support | 2023 |
| Swype Creative Ltd | Professional & scientific | 2023 |
| SX AM Track Limited | Wholesale & retail | 2025 |
| SXF Ltd | Health & social care | 2024 |
| SXJ Services Ltd | Administrative & support | 2022 |
| Sxsd Limited | Wholesale & retail | 2019 |
| SY & N Properties Ltd | Real estate | 2025 |
| SY 57 Ltd | Transport & logistics | 2023 |
| SY Consulting Limited | Information & communication | 2026 |
| SY Fast Food Ltd | Hospitality | 2026 |
| SYA Consulting Ltd | Information & communication | 2019 |
| Syal Group Ltd | Real estate | 2024 |
| Syara Travel Limited | Transport & logistics | 2026 |
| Sycamore Avenue 1966 Limited | Extraterritorial | 2014 |
| Sycamore Court (Sheffield) Management Limited | Households | 2005 |
| Sycamore House Investments Limited | Real estate | 1995 |
| Sycamore Lighting Limited | Wholesale & retail | 1998 |
| Sycamore Products Limited | Extraterritorial | 2014 |
| Sycamore Smiles Ltd | Health & social care | 2025 |
| Sycamore Square Group Ltd | Construction | 2018 |
| Sycom Integrated Solutions Ltd | Information & communication | 2011 |
| Sycom Solutions Ltd | Information & communication | 2022 |
| Sycous Limited | Other services | 2014 |
| Syed 25 Ltd | Hospitality | 2025 |
| Syed G Ltd | Wholesale & retail | 2025 |
| Syed Sultan Limited | Transport & logistics | 2025 |
| Syed's Enterprises Ltd | Wholesale & retail | 2025 |
| Syence Holdings Limited | Financial services | 2026 |
| Syence Limited | Professional & scientific | 2015 |
| Syers Mcgill Limited | Professional & scientific | 2020 |
| Sygnific International Ltd | Wholesale & retail | 2025 |
| SYK Medical Limited | Health & social care | 2022 |
| SYK21 Ltd | Professional & scientific | 2018 |
| Syke Lane Properties Limited | Households | 2002 |
| Sylhet Links Limited | Administrative & support | 2003 |
| Sylvia Health Ltd | Administrative & support | 2024 |
| Sym-Ergy Renewable Energy Limited | Energy | 2024 |
| Symba Limited | Wholesale & retail | 2025 |
| Symbiotic Domestics Limited | Administrative & support | 2008 |
| Symbol Consulting Limited | Information & communication | 2007 |
| Symbollix Limited | Professional & scientific | 2003 |
| Symbyx Ltd | Information & communication | 2019 |
| Symfalogic Accountancy Ltd | Professional & scientific | 2014 |
| Symfalogic Consulting Ltd | Administrative & support | 2023 |
| Symfalogic Corporation Ltd | Real estate | 2013 |
| Symfalogic Ecosystem Ltd | Professional & scientific | 2026 |
| Symington's (Holdings) Limited | Financial services | 2013 |
| Symington's Limited | Manufacturing | 1990 |
| Symonds Safety Associates Limited | Professional & scientific | 2017 |
| Symphony Retail Ltd | Wholesale & retail | 2014 |
| SYN Properties Limited | Real estate | 2020 |
| Synaisis Limited | Information & communication | 2024 |
| Synap Learning Limited | Information & communication | 2014 |
| Synapminds Ltd | Information & communication | 2025 |
| Synapse Partners Limited | Administrative & support | 2022 |
| Sync Social Ltd | Professional & scientific | 2023 |
| Synchro Electrics Ltd | Construction | 2023 |
| Syncopatico Ltd | Information & communication | 2026 |
| Syncotech Digital Ltd | Information & communication | 2016 |
| Syncramesh Ltd | Information & communication | 2025 |
| Syncro Ltd | Information & communication | 2026 |
| Syncvave Ltd | Information & communication | 2026 |
| Syncvr Medical UK Ltd | Information & communication | 2021 |
| Syndicate Creative Limited | Professional & scientific | 2014 |