| Tractable Ltd | Greater London |
| Traction Charger Company Ltd | Wiltshire |
| Tracware Ltd | Isle of Wight |
| Trade & Investment Wales | |
| Trade Finance Global | |
| Trade Interchange Ltd | North Yorkshire |
| Trade Laptop Repairs | |
| Trade Scanners | Buckinghamshire |
| Trade Web Solutions Ltd | Derbyshire |
| Trade-Soft | |
| Tradeteq | |
| Trading Apps Ltd | |
| TradingHub | |
| TradingView | |
| Traffic Digital | Greater London |
| Traffic Giant | Edinburgh |
| Trafiki Ecommerce | Greater London |
| Trailblazer360 | |
| Train Effective Ltd | |
| Traineasy | Buckinghamshire |
| Training Link | Staffordshire |
| Trainline.com Ltd | |
| Trait Media Ltd | |
| Trajital | |
| TrakCel | |
| Traktion Technologies Ltd | |
| Trameto Ltd | |
| Tramshed Tech | |
| Tranex Telecommunications Ltd | Northamptonshire |
| Trans Spectra Ltd | Staffordshire |
| Transcend Marketing | |
| Transcendit Ltd | Tyne and Wear |
| Transdermal Diagnostics | |
| Transeo Media Ltd | |
| TransferGo Ltd | |
| TransFICC | |
| Transfinite Systems Ltd | Greater London |
| Transform Comms | |
| Transform Communications Ltd | |
| Transformify Ltd | |
| Transition | Surrey |
| Transition Computing Ltd | Buckinghamshire |
| Transition Global Management Ltd | |
| Translucent Ltd | |
| TransMedia Dynamics Ltd | Buckinghamshire |
| Transonics plc | Hertfordshire |
| Transparent Intelligence, Inc. | |
| TransparentChoice Ltd | |
| Transparity | |
| Transport Media | |