| TN Network Services Limited | Education | 2023 |
| TN Petroleum Limited | Wholesale & retail | 2023 |
| TN Retail Limited | Wholesale & retail | 2021 |
| TNA Consulting Services Ltd | Information & communication | 2015 |
| TND Lighting Limited | Administrative & support | 2022 |
| TNL Real Estate Ltd | Real estate | 2025 |
| TNT Fireworks Newport Limited | Wholesale & retail | 2025 |
| Toasted at J9 Ltd | Hospitality | 2026 |
| Toasted by Kels Ltd | Hospitality | 2025 |
| Toasted Events Ltd | Hospitality | 2026 |
| Toasty Orchid Limited | Information & communication | 2024 |
| TOBIN85 Ltd | Transport & logistics | 2025 |
| Tocad Limited | Transport & logistics | 2023 |
| Together Again Festival Ltd | Arts & recreation | 2025 |
| Together Events Ltd | Arts & recreation | 2025 |
| Together Professional Services Limited | Professional & scientific | 2011 |
| Tohmie Limited | Health & social care | 2024 |
| Tolfers Ltd | Construction | 2025 |
| TOM Griffin Learning Design Ltd | Education | 2022 |
| TOM K Services Ltd | Transport & logistics | 2026 |
| TOM Wiggans Sound Engineering Limited | Other services | 2003 |
| Tomasulo Construction Limited | Construction | 2005 |
| Tommy LUX Ltd | Wholesale & retail | 2020 |
| Tomos Grace Limited | Real estate | 2024 |
| Tomos Williams Ltd | Arts & recreation | 2022 |
| Toms Autos Ltd | Wholesale & retail | 2024 |
| Toneheld Ltd | Information & communication | 2022 |
| Tonesource Ltd | Information & communication | 2020 |
| Tonks Property Holdings Ltd | Real estate | 2024 |
| Tonks Property Investments Ltd | Administrative & support | 2024 |
| Tony COX Limited | Real estate | 1979 |
| Top Cases Limited | Wholesale & retail | 2022 |
| Top Class Bicycle Repairs Ltd | Other services | 2025 |
| Top Glazing Solutions Ltd | Construction | 2025 |
| Top Midlands Trading AS Taste of Paradise Limited | Hospitality | 2022 |
| Top Nail Beauty Ltd | Other services | 2021 |
| Top Protection Limited | Administrative & support | 2015 |
| Top Renovations Newport Ltd | Construction | 2024 |
| Top Rugby Limited | Arts & recreation | 2025 |
| Top Shop Market NP20 Limited | Wholesale & retail | 2024 |
| Top Taste Pizza and Kebab Ltd | Hospitality | 2018 |
| Top TIA Cleaning Ltd | Administrative & support | 2024 |
| Top Turkish Barbers Ltd | Other services | 2024 |
| Top UPS Convenience Store Properties Ltd | Wholesale & retail | 2022 |
| Top-Notch Care Limited | Health & social care | 2018 |
| Topa Top Recordz Ltd | Information & communication | 2026 |
| Topaz Investment Group Ltd | Real estate | 2025 |
| Topline Retail Solutions Ltd | Wholesale & retail | 2018 |
| Toptiles Ltd | Manufacturing | 2025 |
| TOR Sports Ltd | Manufacturing | 2021 |
| Torese Ltd | Construction | 2014 |
| Torfaen Solar Power Limited | Manufacturing | 2011 |
| Torjesen Events Limited | Administrative & support | 2024 |
| Torjesen Limited | Professional & scientific | 2024 |
| Torque Monsters Limited | Wholesale & retail | 2023 |
| Torty Limited | Hospitality | 2020 |
| Torwen Labs Ltd | Information & communication | 2025 |
| Total Asia Food Limited | Wholesale & retail | 2013 |
| Total Asia Group Ltd | Financial services | 2025 |
| Total Care Maintenance & Construction Limited | Construction | 2003 |
| Total Construction Gwent Limited | Construction | 2019 |
| Total Protection Fire & Security Ltd. | Administrative & support | 2021 |
| Total Recon Ltd | Health & social care | 2025 |
| Total Spray Solutions Limited | Construction | 2013 |
| Total, Theatre, Events and Productions Ltd | Arts & recreation | 2016 |
| Totemo Code Limited | Information & communication | 2018 |
| Tots Play UK Ltd | Wholesale & retail | 2015 |
| Tousles Ltd | Other services | 2018 |
| Tovey Services Limited | Agriculture & fishing | 2011 |
| TP Financial Planning Limited | Professional & scientific | 2017 |
| TP Properties Newport Ltd | Real estate | 2026 |
| TP7 Promotions Limited | Arts & recreation | 2023 |
| TPS Construction (South Wales) Limited | Construction | 2025 |
| TPS Environmental Ltd | Water & waste | 2025 |
| TPT PMM 2024 Limited | Financial services | 2016 |
| TR11 Promotions Ltd | Arts & recreation | 2026 |
| TR19 Grease Ventilation Clean and Technician Ltd | Administrative & support | 2024 |
| Tracktek Rail Support Limited | Administrative & support | 2017 |
| Tracktriklogistics Limited | Transport & logistics | 2025 |
| Tractor Hire Holdings Limited | Financial services | 2026 |
| Tractor Hire Limited | Administrative & support | 1989 |
| Tractor Hire UK Limited | Professional & scientific | 2008 |
| Trade Price Tyres Limited | Wholesale & retail | 2015 |
| Trade Right Motors Ltd | Wholesale & retail | 2025 |
| Trade Shoes Limited | Wholesale & retail | 2007 |
| Trademarksound Ltd | Information & communication | 2023 |
| Tradespeople Ltd | Wholesale & retail | 2020 |
| Tradewinds Global Limited | Information & communication | 2012 |
| Trading Post Abergavenny Ltd | Hospitality | 2019 |
| Traditional Pubs IW Limited | Hospitality | 2014 |
| Trafalgar Court (Newport) Management Company Limited | Real estate | 2010 |
| Traffic Banksman Specialists Ltd | Construction | 2018 |
| Trafficflow Ltd | Construction | 2023 |
| Trafford Associates Limited | Administrative & support | 2017 |
| Traject Ventures Limited | Information & communication | 2021 |
| Tran GIA 2025 Ltd | Wholesale & retail | 2025 |
| Tranquilo Landscapes Ltd | Administrative & support | 2015 |
| Transept Construction Services Ltd | Construction | 2015 |
| Transmar Logistics Ltd | Transport & logistics | 2026 |
| Transolutions Shropshire Ltd | Administrative & support | 2019 |