| Svsec Ltd | Professional & scientific | 2023 |
| Svsh Ltd | Wholesale & retail | 2024 |
| Svtk Ltd | Wholesale & retail | 2025 |
| SW Care Group Ltd | Health & social care | 2018 |
| SW Domiciliary Care Ltd | Health & social care | 2018 |
| SW International Consulting Limited | Administrative & support | 2019 |
| Swailes Family Estates Limited | Real estate | 2019 |
| Swailes of Chelsea Limited | Construction | 2017 |
| Swailes of Oxford Limited | Construction | 2017 |
| Swailes Suites Limited | Construction | 2014 |
| Swain Projects Limited | Professional & scientific | 2003 |
| Swalecliffe Pharmacy Limited | Wholesale & retail | 1999 |
| Swallow Flight Centres Limited | Arts & recreation | 1990 |
| Swan Portaforge Limited | Manufacturing | 2011 |
| Swanbrook Estates Limited | Construction | 2019 |
| Swanbrook Services Limited | Real estate | 1949 |
| Swani Driving School Limited | Education | 2025 |
| Swansea City Access Limited | Extraterritorial | 2025 |
| Swansea North DC Limited | Information & communication | 2025 |
| Swansea North Green NG Limited | Financial services | 2022 |
| Swansea Villas Management Company Limited | Households | 2010 |
| Swarez Art Academy Ltd | Education | 2025 |
| Sweat Guard Ltd | Wholesale & retail | 2006 |
| Sweat the Crazy OUT Ltd | Arts & recreation | 2024 |
| Sweeney TOM Ltd | Other services | 2016 |
| Sweet Silent Disco Ltd | Health & social care | 2026 |
| Sweet Success Catering Ltd | Hospitality | 2025 |
| Swift Art & Design Limited | Wholesale & retail | 2024 |
| Swift BFP Limited | Financial services | 2009 |
| Swift Court and Morris Walk Management Company Limited | Households | 2018 |
| Swift Electrical (SW) Ltd | Construction | 2020 |
| Swift Lodde Property Ltd | Construction | 2023 |
| Swiftfleet Enterprises Ltd | Transport & logistics | 2025 |
| Swim Consult Ltd | Other services | 2017 |
| Swim Design Space Limited | Arts & recreation | 2021 |
| Swim Secure Limited | Wholesale & retail | 2016 |
| SWIM2SCHOOLS Limited | Education | 2025 |
| Swimlane UK Ltd | Information & communication | 2019 |
| Swimming by Design Ltd | Education | 2012 |
| Swindon Close (Cheltenham) RTM Company Limited | Households | 2012 |
| Swindon Manor Management Company Limited | Households | 1997 |
| Swindon Vehicle Solutions Limited | Wholesale & retail | 2008 |
| Swinhay Yarrow Limited | Professional & scientific | 2020 |
| Swissex Group Ltd | Professional & scientific | 2024 |
| Switch Electrical & Building Contractors Ltd | Construction | 2017 |
| Swon Ltd | Wholesale & retail | 2021 |
| Sword Developments Limited | Wholesale & retail | 2008 |
| Swords Digital Ltd | Professional & scientific | 2021 |
| Swpg Developments Limited | Construction | 2022 |
| Swpg Rock Limited | Real estate | 2021 |
| Swpg Stroud Limited | Real estate | 2022 |
| SWS International Limited | Wholesale & retail | 1999 |
| Swsi Limited | Financial services | 2019 |
| SXS Design & Build Ltd | Construction | 2019 |
| Syacamore Guernsey Limited | | 2023 |
| Sybic Limited | Administrative & support | 2007 |
| Sycamore Guernsey Limited | | 2024 |
| Syco Labs Ltd | Information & communication | 2022 |
| SYL Cheltenham Ltd | Hospitality | 2024 |
| Sylhet Chai Limited | Hospitality | 2026 |
| Sylvan Consultancy Limited | Professional & scientific | 2023 |
| Symbiometry Ltd | Information & communication | 2021 |
| Symbioss Ltd | Professional & scientific | 2024 |
| Symmetry Projects Ltd | Information & communication | 2015 |
| Symonds of Hereford Limited | Wholesale & retail | 2011 |
| Symprest Holdings Limited | Financial services | 2023 |
| Symprest Limited | Information & communication | 2023 |
| Synalogik Innovative Solutions Limited | Information & communication | 2018 |
| Synaptica Consulting Limited | Professional & scientific | 2021 |
| Synergi Consulting Group Ltd | Professional & scientific | 2019 |
| Synergos Developments Ltd | Real estate | 2023 |
| Synergy BPE Developments Ltd | Construction | 2025 |
| Synergy BPE Ltd | Construction | 2023 |
| Synergy BPE Property Ltd | Real estate | 2024 |
| Synergy IT Solutions Limited | Wholesale & retail | 2012 |
| Synergy Safeguarding Ltd | Professional & scientific | 2025 |
| Synergy Search Global Limited | Administrative & support | 2025 |
| Synlatex Limited | Wholesale & retail | 2018 |
| Synq. Accounting and Advisory Limited | Professional & scientific | 2025 |
| Syntech Science Ltd | Information & communication | 2024 |
| Syntergy Limited | Professional & scientific | 2010 |
| Synthesis Films Ltd | Information & communication | 2024 |
| Synthetic Culture Limited | Other services | 2015 |
| Syon Property Services Ltd | Real estate | 2018 |
| Syreford Quarries & Masonry Limited | Mining & quarrying | 2005 |
| Syreford View Farm Ltd | Agriculture & fishing | 2019 |
| Sysarm Ltd | Professional & scientific | 2013 |
| Systems Cubed Ltd | Information & communication | 2025 |
| Systems for Dentists Limited | Information & communication | 1987 |
| Systems in Technology Ltd | Information & communication | 2013 |
| Systems Technology (Holdings) Limited | Professional & scientific | 2002 |
| Systems Technology (S.E.) Limited | Wholesale & retail | 1988 |
| Syvretmedia Limited | Professional & scientific | 2008 |
| T & B Danter Leisure Ltd | Arts & recreation | 2006 |
| T & JH Holdings Ltd | Financial services | 2024 |
| T and J Martin Ltd | Agriculture & fishing | 2011 |
| T B Produce Limited | Agriculture & fishing | 2013 |
| T Ball & Sons Roofing Limited | Construction | 2021 |
| T Costello Building Services Limited | Construction | 2006 |
| T G Cars Limited | Wholesale & retail | 2025 |