| Swindon's Food Collective Ltd | Hospitality | 2018 |
| SWINDON121 Restaurant Ltd | Hospitality | 2025 |
| Swindonpickleball Community Interest Company | Education | 2025 |
| Swindonrenovations Ltd | Construction | 2025 |
| Swindonrepairs Limited | Wholesale & retail | 2025 |
| Swindonspartans Ltd | Arts & recreation | 2025 |
| Swindonweb Design Limited | Information & communication | 2005 |
| Swindonweb LLP | | 2002 |
| Swing Away Tents Ltd | Extraterritorial | 2023 |
| Swinprop Limited | Real estate | 2015 |
| Swinsoft Limited | Information & communication | 2015 |
| Swinton & Eleanora Ltd | Administrative & support | 2023 |
| Swinton Reds 20 Limited | Professional & scientific | 2013 |
| Swipe Marketing Limited | Professional & scientific | 2024 |
| Swisan Creations Ltd | Arts & recreation | 2024 |
| Swiss Chalet Swindon Limited | Hospitality | 2025 |
| Switch on Computers Ltd | Information & communication | 2015 |
| Switch on Group Ltd | Information & communication | 2012 |
| Swithin Lane Advisory Ltd | Professional & scientific | 2025 |
| Swoop Learning Limited | Education | 2024 |
| Sword Gardens 1963 Limited | Extraterritorial | 2013 |
| SWT Productions Limited | Information & communication | 2013 |
| Syamic Solutions Ltd | Information & communication | 2020 |
| Sydney Maurice Ltd | Professional & scientific | 2021 |
| Sydney Maurice U.K Ltd | Wholesale & retail | 2025 |
| Sylwood Ltd | Hospitality | 2018 |
| Symantix Ltd | Information & communication | 2006 |
| Symitech Limited | Manufacturing | 2019 |
| Symphonie Limited | Financial services | 2020 |
| Synapse Logistics Ltd | Wholesale & retail | 2025 |
| Sync Guarding Management Ltd | Information & communication | 2024 |
| Syndicate Alpha Ltd | Hospitality | 2020 |
| Syneargy Limited | Information & communication | 2023 |
| Synister Music Events Limited | Public administration | 2017 |
| Syntacta Ltd | Professional & scientific | 2010 |
| Syon Hira Property Ltd | Real estate | 2023 |
| Syscom Tech Ltd | Information & communication | 2013 |
| Sysflex Ltd | Information & communication | 2020 |
| Systec Systems Limited | Professional & scientific | 2026 |
| System Four Ltd | Professional & scientific | 2025 |
| Systems Test Solutions Limited | Information & communication | 2005 |
| Systemus Ltd | Professional & scientific | 2024 |
| Systicia Ltd | Information & communication | 2007 |
| SZ Fire Ltd | Construction | 2018 |
| Szenta Andrei Ltd | Transport & logistics | 2016 |
| SZK Leisure Ltd | Hospitality | 2026 |
| SZN Traders Ltd | Wholesale & retail | 2025 |
| T & B Recycling Limited | Water & waste | 2021 |
| T & C Home Improvements Ltd | Construction | 2020 |
| T & I Property Limited | Real estate | 2018 |
| T & J Properties (Swindon) Limited | Real estate | 2018 |
| T & S Electrical Engineers Limited | Construction | 2023 |
| T & T Developments Ltd | Construction | 2021 |
| T a Reed (Wiltshire) Ltd | Information & communication | 2017 |
| T Bush Limited | Other services | 2024 |
| T Charlton Ltd | Construction | 2024 |
| T G Precision Limited | Professional & scientific | 2010 |
| T James Electrical Projects Limited | Construction | 2012 |
| T James Motors Limited | Wholesale & retail | 2021 |
| T Lebas Rail Limited | Transport & logistics | 2018 |
| T Parker-Royle Ltd | Information & communication | 2022 |
| T&B P.Dev. & Recycling (Swindon) Limited | Water & waste | 2006 |
| T&D Estates Ltd | Construction | 2021 |
| T&G Care Limited | Administrative & support | 2018 |
| T&G Ltd | Manufacturing | 2020 |
| T&P Decorating Ltd | Construction | 2026 |
| T&S Wisdom UK Ltd | Wholesale & retail | 2018 |
| T.D. Williamson (U.K.) Limited | Manufacturing | 1964 |
| T.D. Williamson UK International Limited | Professional & scientific | 2014 |
| T.E.N.G-E Nexus Limited | Transport & logistics | 2024 |
| T.F.E.E. Limited | Information & communication | 2003 |
| T.G. Jeary (Holdings) Limited | Real estate | 1940 |
| T.G. Jeary Limited | Real estate | 1961 |
| T.H. Burroughs Family Butchers LLP | | 2008 |
| T.I.E. Ltd | Professional & scientific | 2020 |
| T.L.H.E Group Ltd | Hospitality | 2020 |
| T.S Clothing Limited | Health & social care | 2015 |
| T.W.Gore(Farms)Limited | Agriculture & fishing | 1958 |
| T2 Awards Limited | Other services | 2020 |
| T2 Fitness Training & Education Limited | Arts & recreation | 2013 |
| T3 Project Management Limited | Professional & scientific | 2025 |
| T3MS Property Group Limited | Real estate | 2026 |
| T4 Cameras Limited | Wholesale & retail | 1994 |
| TA Gemini Solutions Limited | Information & communication | 2014 |
| TA Gynae Limited | Health & social care | 2022 |
| TA Sport Stars Ltd | Arts & recreation | 2021 |
| Taashi Crown Limited | Hospitality | 2018 |
| Tabaah Ltd | Health & social care | 2023 |
| Tablehill Limited | | 1985 |
| Tabolan Ltd | Health & social care | 2023 |
| Tachology Digital Limited | Information & communication | 2024 |
| TACT07 Ltd | Transport & logistics | 2022 |
| Tadeda Limited | Professional & scientific | 2021 |
| Tadmud Limited | Arts & recreation | 2014 |
| TAE Power Solutions Engineering Limited | Professional & scientific | 2018 |
| TAE Power Solutions Limited | Other services | 2021 |
| TAE Power Solutions Manufacturing Limited | Manufacturing | 2019 |
| Taekwondo Council United Kingdom | Arts & recreation | 2020 |
| Tahtech Ltd | Wholesale & retail | 2025 |
| Tailored Data Solutions Ltd. | Administrative & support | 2015 |