| Transform Communications Ltd | |
| Transformify Ltd | |
| Transition | Surrey |
| Transition Computing Ltd | Buckinghamshire |
| Translucent Ltd | |
| TransMedia Dynamics Ltd | Buckinghamshire |
| Transonics plc | Hertfordshire |
| Transparent Intelligence, Inc. | |
| TransparentChoice Ltd | |
| Transparity | |
| Transport Media | |
| Transys Electronics Ltd | Warwickshire |
| Travco Corporation Ltd | |
| Travel Technology Systems Ltd | Lancashire |
| Travellar | |
| TravelLocal Ltd | |
| Travelnest | |
| Traveltech for Scotland | |
| TRC Data Recovery Ltd | South Yorkshire |
| TRCREATIVE | |
| TRDATA Technology Ltd | |
| treaclemedia Ltd | Surrey |
| TreasurySpring Ltd | |
| Tred Earth Ltd | |
| Treefera Operations Ltd | |
| TreeFrog Software | |
| Treetoscope Ltd | |
| Treken | Dorset |
| TREND Networks | |
| Treos Bio Ltd | |
| Tres Tria Ltd | Kent |
| Trevisan Ltd | |
| Trevor Peters Design Ltd | Wiltshire |
| Trevor.io | |
| TRG Design | Devon |
| Tri Computers | Berkshire |
| Tri Technology | Nottinghamshire |
| Tri-it Ltd | |
| Tri-Tech 3D Ltd | |
| Triad Group plc | Surrey |
| Triad Ltd | |
| Triage Services Ltd | Bedfordshire |
| Trial Systems | |
| Triangle Digital Support | North Yorkshire |
| Triangle Software | Cheshire |
| Triangular Pixels Ltd | |
| Triarom Computers | |
| Triaster Ltd | Oxfordshire |
| Triax UK Ltd | Rhondda Cynon Taf |
| Tribal Ltd | Berkshire |