| Surveys Gwalia CYF | Professional & scientific | 2008 |
| SW Property Renovations Ltd | Construction | 2024 |
| SW3 Media Limited | Information & communication | 2024 |
| Swanbridge Supplies Ltd | Wholesale & retail | 2023 |
| Sweet Espresso Ltd | Hospitality | 2025 |
| Swn/Sound Limited | Information & communication | 2012 |
| Synergy Scaffold UK Ltd | Construction | 2023 |
| T & Co Consultancy Ltd | Professional & scientific | 2020 |
| T J Moore Limited | Professional & scientific | 2025 |
| Tacs Cardiff Limited | Professional & scientific | 2000 |
| Tailored Solutions Recruitment Limited | Administrative & support | 2004 |
| Tairona Innovation Limited | Financial services | 2026 |
| Tairona Ventures Ltd | Financial services | 2026 |
| Tale Chasing Ltd | Administrative & support | 2025 |
| Talent Matters Limited | Professional & scientific | 2004 |
| Tannorella Mortgages Ltd | Financial services | 2014 |
| TAS Media Limited | Wholesale & retail | 2021 |
| Tatu Pictures Ltd | Information & communication | 2014 |
| Tea and Biscuit Homes Ltd | Real estate | 2020 |
| Teagle Investments Ltd | Real estate | 2023 |
| Team Draig Limited | Arts & recreation | 2022 |
| Teasel 1990 Limited | Extraterritorial | 2014 |
| TEC Marina Ltd | Real estate | 2015 |
| Tech for Togs Limited | Wholesale & retail | 2021 |
| Techni-Flow (UK) Limited | Manufacturing | 1992 |
| Technical and Design Engineering Limited | Construction | 2014 |
| Technical Marketing & PR Ltd | Administrative & support | 2011 |
| Technician Hall Ltd | Other services | 2025 |
| Tegan Holdings Ltd | Real estate | 2017 |
| Tenancy Partners Cardiff Ltd | Real estate | 2026 |
| Tennis Squad Limited | Arts & recreation | 2015 |
| TES Interiors Ltd | Construction | 2016 |
| Tescons Ltd | Transport & logistics | 2017 |
| Tesoro MIO Ltd | Hospitality | 2025 |
| Testament Health and Wellness Ltd | Health & social care | 2024 |
| Testing Saints Ltd | Professional & scientific | 2024 |
| TH Sport Ltd | Education | 2019 |
| THE A2B Tyre Shop Limited | Wholesale & retail | 2018 |
| THE Angel Collective Group Ltd | Wholesale & retail | 2024 |
| THE Angel Healing Collective CIC | Other services | 2025 |
| THE Beach Caravan Park Company Limited | Hospitality | 1995 |
| THE Beauty Spot Cafe Limited | Hospitality | 2021 |
| THE Bike Shop (Wales) Limited | Wholesale & retail | 2014 |
| THE Cambrian Gallery Limited | Wholesale & retail | 2000 |
| THE Cat Lady Ltd | Other services | 2025 |
| THE Cbva Clinic Ltd | Health & social care | 2024 |
| THE Ditari Lente Company Limited | Wholesale & retail | 2026 |
| THE Female Touch Garden Design and Maintenance Ltd | Other services | 2025 |
| THE Good Wash Enterprise CIC | Other services | 2018 |
| THE Goodwash Trading Company Ltd | Wholesale & retail | 2021 |
| THE Grand Cardiff Management Company Limited | Real estate | 2003 |
| THE Green Room (Penarth) Limited | Wholesale & retail | 2021 |
| THE Guildhall Carmarthen Ltd | Administrative & support | 2018 |
| THE Hair Business of Cowbridge Limited | Other services | 2005 |
| THE Haven Spa Limited | Other services | 2002 |
| THE High Street Group Ltd | Other services | 2025 |
| THE Jazz and Blues Joint Enterprise CIC | Education | 2025 |
| THE King PIN Emporium Limited | Wholesale & retail | 2020 |
| THE Level Support CIC | Education | 2026 |
| THE Lewis Property Group Ltd | Real estate | 2020 |
| THE Life of Reilly Collection Ltd | Hospitality | 2025 |
| THE Lodge (Penarth) RTM Limited | Households | 2017 |
| THE Lucky Leprechaun Limited | Hospitality | 2017 |
| THE Luxury Hospitality Group Ltd | Hospitality | 2009 |
| THE Media Angel (UK) Ltd | Professional & scientific | 2012 |
| THE Mini Social Club Ltd | Hospitality | 2026 |
| THE Monico RTM Company Limited | Real estate | 2010 |
| THE Murmur (DP) Ltd | Hospitality | 2026 |
| THE Natural Pet Pantry Ltd | Wholesale & retail | 2020 |
| THE Polka DOT Door Ltd | Wholesale & retail | 2008 |
| THE Priory (Llandough) Residents Management Company Limited | Households | 2014 |
| THE Queen B Boutique Limited | Wholesale & retail | 2009 |
| THE Red Balloon Company Limited | Arts & recreation | 1987 |
| THE Regal Mutt Limited | Wholesale & retail | 2013 |
| THE Restaurant Marine Parade Worthing Ltd | Hospitality | 2018 |
| THE Rogue Welsh Cake Company Ltd | Hospitality | 2020 |
| THE Solopreneur Awards Ltd | Administrative & support | 2025 |
| THE Spark Movement CIC | Education | 2024 |
| THE Spinney Holiday & Leisure Park Limited | Hospitality | 1992 |
| THE Three Amigo's Limited | Hospitality | 1999 |
| THE Valleywood Group Ltd | Professional & scientific | 2018 |
| THE Washington Butchers Ltd | Hospitality | 2021 |
| THE Waverley Care Centre Limited | Health & social care | 2000 |
| THE Welsh Chef Limited | Hospitality | 2024 |
| THE Windsor (Penarth) Masonic Hall Company (1927) Limited | Hospitality | 1927 |
| Thegeekcompany Limited | Other services | 2021 |
| Thisisus.Digital Ltd | Professional & scientific | 2022 |
| Thomas IVY Developments Ltd | Construction | 2017 |
| Thomas Property Developers Ltd | Real estate | 2017 |
| Thompson Court Management Co. Limited | Households | 1986 |
| Thompson Young Properties Ltd | Real estate | 2022 |
| Thor Developments (UK) Limited | Construction | 2015 |
| Thor Electrical Installations Limited | Construction | 2025 |
| Ticketsource Limited | Arts & recreation | 2004 |
| Tidy Living Company Ltd | Administrative & support | 2023 |
| Tiger Bay Investments Limited | Real estate | 2004 |
| Timaru Engineering Limited | Professional & scientific | 2000 |
| Time and Oath Limited | Professional & scientific | 2021 |
| Time to EAT Penarth Ltd | Hospitality | 2025 |
| Timeless Bathrooms Ltd | Construction | 2025 |