| Thomas Arthur Consulting Ltd | Professional & scientific | 2025 |
| Thomas Kitchens and Building Solutions Ltd | Construction | 2019 |
| Thomas,Mills & Co.,Limited | Wholesale & retail | 1958 |
| Thompson's (Porthcawl) Limited | Real estate | 2003 |
| Thooshan Ltd | Manufacturing | 2026 |
| Thorne Technology Ltd | Information & communication | 2024 |
| Thornes Pharma Holdings Limited | Wholesale & retail | 2018 |
| Thornes Pharmacy Limited | Health & social care | 2007 |
| Thornfield Mews Management Company Limited | Real estate | 2002 |
| Three Horse Shoes Cefn Cribwr Limited | Hospitality | 2017 |
| Thrive Marketing Solutions Limited | Professional & scientific | 2026 |
| Thrivehrm Ltd | Administrative & support | 2023 |
| Tidy Building Company Ltd | Construction | 2023 |
| Tikataco Ltd | Hospitality | 2019 |
| Tilbury Corporations Limited | Real estate | 2009 |
| Tiles Today Limited | Construction | 2014 |
| Tilton Developments Limited | Construction | 2007 |
| TIM Vaughan Racing Limited | Arts & recreation | 2006 |
| TIN HAT Productions Limited | Information & communication | 2013 |
| Tinnelly Estates Limited | Construction | 2015 |
| Tiny Town Bridgend Ltd | Hospitality | 2026 |
| Titan Garden Services Ltd | Administrative & support | 2022 |
| Titorich Chicken House Manokan Ltd | Hospitality | 2016 |
| TJ Access Control Systems Limited | Professional & scientific | 2018 |
| TJ Services (Wales) Limited | Manufacturing | 2004 |
| TJ Services Investments Ltd | Financial services | 2023 |
| TJJ Properties Limited | Real estate | 2012 |
| TJW Builders Limited | Construction | 2020 |
| TJW Property & Development Limited | Real estate | 2023 |
| TMG Holdings and Investments Ltd | Construction | 2023 |
| Tmtt Ltd | Wholesale & retail | 2024 |
| TNR Property Sourcing Ltd | Administrative & support | 2024 |
| TOCC22 Limited | Manufacturing | 2022 |
| Today Finance Limited | Financial services | 1971 |
| Toddler Sense Bridgend Ltd | Health & social care | 2025 |
| Todo Payments Ltd | Information & communication | 2019 |
| Togz Corporations Ltd | Construction | 2021 |
| Tojosa Ltd | Extraterritorial | 2016 |
| Tollgate Engineering Services Ltd | Construction | 2019 |
| TOM Pugh Contracting Limited | Agriculture & fishing | 2025 |
| TOM Pugh Holdings Limited | Financial services | 2025 |
| TOM Pugh Plant Hire Limited | Administrative & support | 2025 |
| TOM Rich Creative Limited | Manufacturing | 2015 |
| Tondu Cricket Club Trading Limited | Arts & recreation | 2016 |
| Tondu Rugby Football Club Limited | Arts & recreation | 2015 |
| Tondu United Football Club CIC | Education | 2020 |
| Tonebeck Limited | Information & communication | 2024 |
| Tonebest Limited | Extraterritorial | 2026 |
| Tonic Studios Limited | Wholesale & retail | 2000 |
| Tool Haven Ltd | Wholesale & retail | 2023 |
| TOOLK-1T Ltd | Information & communication | 2020 |
| Topbourne Limited | Extraterritorial | 2026 |
| Topbridge Limited | Extraterritorial | 2026 |
| Topclay Limited | Agriculture & fishing | 2025 |
| Topex Limited | Transport & logistics | 2005 |
| Torovida Limited | Real estate | 2021 |
| Torque UP Ltd | Professional & scientific | 2024 |
| Totah Engineering Limited | Construction | 2025 |
| Total Fabrication Services (Wales) Limited | Manufacturing | 2010 |
| Total Facade Systems Limited | Construction | 2017 |
| Totale OPS Ltd | Financial services | 2017 |
| Totoro Properties Limited | Real estate | 2024 |
| Toucan Contracting Limited | Manufacturing | 2016 |
| Touchstone Support Services Ltd | Health & social care | 2021 |
| Tovey Developments Limited | Construction | 2020 |
| Towbar and Leisure Solutions Limited | Wholesale & retail | 2019 |
| Towbar Solutions Wales Ltd | Wholesale & retail | 2022 |
| Town & Suburban (Properties) Limited | Construction | 1959 |
| Town and Country (Wales) Limited | Administrative & support | 2007 |
| Town and Country Bedrooms Limited | Wholesale & retail | 2010 |
| Toymeetsworld Limited | Wholesale & retail | 2015 |
| TPM Plumbing Ltd | Construction | 2022 |
| TQS Business Solutions Ltd | Administrative & support | 2011 |
| TR Leisure Consulting Ltd | Hospitality | 2026 |
| Trade Landscape Supplies Ltd | Wholesale & retail | 2023 |
| Trade Price Aluminium Limited | Manufacturing | 2018 |
| Tradesmen Direct Limited | Administrative & support | 2015 |
| Traedium Limited | Construction | 1999 |
| Trailerman Limited | Wholesale & retail | 2003 |
| Training Services (Wales) Ltd | Education | 2009 |
| Training Solutions (Wales) Ltd | Extraterritorial | 2009 |
| Transgas Limited | Professional & scientific | 1997 |
| Transport and Plant Control Limited | Administrative & support | 2005 |
| Transport for Life Ltd | Wholesale & retail | 2007 |
| Trauma Nursing Limited | Education | 2006 |
| Treadmark Limited | Administrative & support | 2007 |
| Treatment Working Limited | Real estate | 2024 |
| Tredwr Renovations & Rentals Ltd | Real estate | 2022 |
| Treforest Tiling Limited | Construction | 1973 |
| Trendy Film Limited | Information & communication | 2015 |
| Trentfox Limited | Extraterritorial | 2025 |
| TRI Cymru Developments Ltd | Construction | 2025 |
| Triangle Developments (Wales) Limited | Construction | 2026 |
| Triangle Property (Cowbridge) Limited | Households | 1947 |
| Triangle Property Holdings Limited | Real estate | 2015 |
| Triangles Bridgend Limited | Hospitality | 2020 |
| Trident Damp Solutions Ltd | Construction | 2024 |
| Trident Services Ltd | Education | 2025 |
| Trimtabs Ltd | Professional & scientific | 2019 |
| Trinity Bookkeeping Ltd | Professional & scientific | 2023 |