| Susrec Limited | Professional & scientific | 2022 |
| Sustainable Property Solutions Ltd | Professional & scientific | 2025 |
| Suukkosan Limited | Education | 2020 |
| Swansea Competitions Ltd | Arts & recreation | 2025 |
| Swansea Landscaping Supplies Ltd | Wholesale & retail | 2025 |
| Swansea Tattoo Removal’S Ltd | Other services | 2025 |
| Sweet Honey Stationery Limited | Wholesale & retail | 2025 |
| Swiftlink Recruitment Ltd | Administrative & support | 2024 |
| Swihart-Rees Limited | Real estate | 1993 |
| Swimpatico Limited | Wholesale & retail | 2024 |
| Swish Valet Services Limited | | 1988 |
| Swiss Valley Caravans Ltd | Transport & logistics | 2013 |
| Swiss Valley Fish Bar Limited | Hospitality | 2019 |
| Swtj Installations Ltd | Information & communication | 2025 |
| SWV Holdings Limited | Extraterritorial | 2018 |
| SWW Commercial Finance Limited | Financial services | 2013 |
| Sycamore Environmental Ltd | Professional & scientific | 2016 |
| Syddyn Properties Limited | Real estate | 2025 |
| Sykes Energy Services Limited | Construction | 2016 |
| Sylen Lakes Ltd | Other services | 2013 |
| Synergybio Ltd | Wholesale & retail | 2024 |
| SZ1R Ltd | Real estate | 2025 |
| T Eurwyn Jones Ltd | Agriculture & fishing | 2011 |
| T Y Hapus Nurseries Ltd | Health & social care | 2026 |
| T&M Llanelli Ltd | Financial services | 2025 |
| T&P Coalbrook Autos Ltd | Wholesale & retail | 2024 |
| T-Boi Coffee Limited | Manufacturing | 2023 |
| T. a. D. Builders Limited | Construction | 1979 |
| T.E.L. Conversations Limited | Professional & scientific | 2016 |
| T1 Cafe Lounge Ltd | Hospitality | 2021 |
| T1 Management Ltd | Professional & scientific | 2020 |
| Tachocom Ltd | Transport & logistics | 2023 |
| Tadaima Limited | Real estate | 2026 |
| Tafarn Bars Ltd | Hospitality | 2024 |
| Tafarn Pubs Ltd | Hospitality | 2024 |
| Tafarn Y Felin Ltd | Hospitality | 2021 |
| Taffy Skip Hire Ltd | Water & waste | 2025 |
| TAI Property Ltd | Real estate | 2014 |
| Talyfan Contractors Ltd | Construction | 2021 |
| Tammy's Barber Shop Limited | Other services | 2015 |
| Target Zero Limited | Administrative & support | 2010 |
| TAS Plant Hire Ltd | Construction | 2025 |
| Tastenaija Ltd | Wholesale & retail | 2025 |
| Tasty Tatws Ltd | Hospitality | 2025 |
| Tawe Properties Limited | Real estate | 2002 |
| Taylor Facilities Management Ltd | Administrative & support | 2024 |
| Taylor Holdings Group Limited | Real estate | 2024 |
| Taylor Homes (S Wales) Limited | Real estate | 2025 |
| Taylor Landscapes & Grounds Maintenance Limited | Administrative & support | 2013 |
| Taylor Made Carpentry & Handyman Services Limited | Manufacturing | 2023 |
| Taylor Properties Management Ltd | Financial services | 2023 |
| Taylors FM Holdings Limited | Administrative & support | 2026 |
| TBM Creative Ltd | Information & communication | 2021 |
| TCW Group Ltd | Administrative & support | 2020 |
| TCW Training Ltd | Education | 2020 |
| Tea Traders Ltd. | Wholesale & retail | 2017 |
| Teaching Elite Limited | Administrative & support | 2014 |
| Teaching Expenditure Limited | Administrative & support | 2014 |
| TEB Consulting Ltd | Information & communication | 2026 |
| Tebot Limited | Hospitality | 2019 |
| Teddington Components Limited | Manufacturing | 1995 |
| Teddington Distribution Limited | Wholesale & retail | 2015 |
| Teddington Engineered Solutions Ltd | Manufacturing | 2003 |
| Teddington Fabrication Services Limited | Manufacturing | 2014 |
| Teddington Group International Limited | Extraterritorial | 2003 |
| Teddington Holding Company Limited | Financial services | 2014 |
| Tegan Jade Boutique Ltd | Wholesale & retail | 2025 |
| Tegeus Ltd | Other services | 2010 |
| Teko Group Ltd | Professional & scientific | 2024 |
| Teko Holdings Ltd | Financial services | 2025 |
| Teledu Tinopolis CYF | Information & communication | 1994 |
| Television Corporation Consumer Brands Limited | Information & communication | 2002 |
| Television Corporation Productions Limited | Information & communication | 2002 |
| Tenten Construction Ltd | Manufacturing | 2023 |
| Terry Griffiths Matchroom Inc Limited | Arts & recreation | 2012 |
| Tether Digital Ltd | Information & communication | 2020 |
| TH Lush Spa Ltd | Other services | 2015 |
| Thai House Llanelli Ltd | Hospitality | 2018 |
| THE Bell Hospitality Limited | Hospitality | 2026 |
| THE Better Developer Limited | Real estate | 2005 |
| THE Black Book Estate Company Limited | Real estate | 2001 |
| THE Bohemians Theatre Company Ltd | Arts & recreation | 2021 |
| THE Celtic PIE Company Ltd | Extraterritorial | 2009 |
| THE Cleanhouse Services Ltd | Administrative & support | 2016 |
| THE Combat Cleaners Ltd | Administrative & support | 2024 |
| THE Croft Holiday Home Ltd | Hospitality | 2017 |
| THE Crystal Florist Ltd | Wholesale & retail | 2022 |
| THE Direct Cremation Service Company Limited | Health & social care | 2019 |
| THE Doggy Desserts Group Ltd | Manufacturing | 2025 |
| THE Fibre Guys Holdings Ltd | Information & communication | 2022 |
| THE Fibre Guys Ltd | Information & communication | 2018 |
| THE Gowen Group Limited | Real estate | 2024 |
| THE Gower Crepe Company Ltd | Hospitality | 2023 |
| THE Grappling Academy Ltd | Arts & recreation | 2025 |
| THE Half Moon (Llanelli) Limited | Hospitality | 2010 |
| THE House of Atabey Ltd | Wholesale & retail | 2025 |
| THE Inclusive Play Space CIC | Health & social care | 2026 |
| THE Lewis Arms Llanelli Ltd | Hospitality | 2019 |
| THE Little Welsh Deli Ltd | Manufacturing | 2018 |
| THE Means Holdings Limited | Financial services | 2024 |