| Tribus | |
| Trichromic, LLP | Greater London |
| Trickle Data Insights Ltd | |
| Tricostar Software Ltd | |
| Trident BioPharm Solutions | |
| Triducive | |
| Trifle Solution | |
| Trig Avionics Ltd | |
| TRIG Creative Ltd | |
| Trigger.dev | |
| TriggerAppy Ltd | |
| Trilan IT | |
| Trilby Multimedia Ltd | West Midlands |
| Trillenium (UK) Ltd | Greater London |
| Trillium Flow Technologies | |
| Trilogy Communications Ltd | Cambridgeshire |
| Trilogy Group | Gloucestershire |
| Trimast New Media | |
| Trimtech Therapeutics Ltd | |
| Trinity Heriot | Edinburgh |
| Trinity Integrated Systems Ltd | |
| Trinityweb Ltd | |
| TRINT | Greater London |
| Trint Ltd | |
| Trio Medicines Ltd | |
| Trio Motion Technology Ltd | |
| triOpsis Ltd | Buckinghamshire |
| Trip Solutions | |
| Triple Software Ltd | |
| TripStax | |
| Trisk Bio | |
| Trisoft Ltd | Nottinghamshire |
| Trison UK | Hertfordshire |
| Tristan Capital Partners | Greater London |
| Tristar Web Solutions | Hertfordshire |
| Tritec | Hampshire |
| Tritech International Ltd | |
| Triton consulting | Norfolk |
| Triumph Arcade UK Ltd | |
| Triumph Technologies Ltd | Oxfordshire |
| Triver Ltd | |
| TRL Software | |
| TRM International Ltd | Merseyside |
| Trogenix Ltd | |
| Tromero Ltd | |
| TRON Media Ltd | |
| Tron Systems Ltd | West Lothian |
| Tronisoft Ltd | Berkshire |
| Tru-Stories, LLP | |
| Tru.ID | |