| TWR Computing | South Yorkshire |
| TX Corporation Ltd | |
| Txtlocal Ltd | Berkshire |
| Tycom Ltd | Aberdeen |
| Tyder Ltd | Mid-Ulster |
| TYG Oncology Ltd | |
| Tyk Technologies | |
| Tylden Ltd | Hampshire |
| Tyler Lewis | Greater Manchester |
| Tyler Webdesign | Greater London |
| Tymit Ltd | |
| Tyne Metropolitan College | |
| Tyne Tech Repairs | |
| Tyneside Linux User Group | Tyne and Wear |
| Tyntec | |
| Type Prompt | |
| Type Rite 08 Ltd | Newry, Mourne and Down |
| TypeDB | |
| typeTheta | |
| Typharm Ltd | |
| Typhoon Solutions | |
| Tyresoft Ltd | |
| Tyrocirle Ltd | |
| Tyxan Ltd | |
| U Refill Toner Ltd | West Midlands |
| U-Ploid Biotechnologies Ltd | |
| U2A Solutions | |
| UAS Enterprises Ltd | Cornwall |
| Ubamarket Ltd | |
| Über Agency | |
| Uber Digital Ltd | |
| Uberweb | Tyne and Wear |
| UBIO Ltd | Greater London |
| Ubiquigent Ltd | |
| Ubisecure, Inc. | |
| Ubisend | |
| Ubisense | Cambridgeshire |
| Ubuntu | |
| UC4 | West Midlands |
| UCL Business Ltd | |
| UCL Partners | |
| UClimb Ltd | |
| UCS | West Midlands |
| uDream Solutions Ltd | Greater London |
| UENI Ltd | Greater London |
| UENI Ltd | |
| UFMedia | |
| UFO Design | East Sussex |
| Ufonia Ltd | |
| UFORIKA | |