| Top Click Media Ltd | Surrey |
| Top Page SEO | Gloucestershire |
| Top Rank Studio Ltd | Greater Manchester |
| Top Spin Web Design | Worcestershire |
| Top Spot Optimisation | Hertfordshire |
| top5hosting.co.uk | |
| TopSource Worldwide | |
| TopSys-IT | Greater Manchester |
| TopUniversities | Greater London |
| Toqio | |
| Tor Studio Ltd | |
| TOR Systems Ltd | Staffordshire |
| Torchbox | Oxfordshire |
| Torque Solutions Ltd | |
| Total Computer and Network Support Ltd | Warwickshire |
| Total Data Management Ltd | |
| Total Digital | |
| Total Electronic Systems | Dorset |
| Total Enterprise Solutions | |
| Total Frequency Control Ltd | West Sussex |
| Total Integrated Solutions Ltd | Nottinghamshire |
| Total Labelling Solutions Ltd | Tyne and Wear |
| Total Network Technologies Ltd | Norfolk |
| Total Registrations | Greater Manchester |
| Total Results Ltd | Tyne and Wear |
| Total Security Ltd | |
| Total SEO & Marketing Ltd | |
| Total SEO Services | South Yorkshire |
| Total Systems plc | |
| Total Technology | Hertfordshire |
| Total Telephone Solutions | |
| Total Training Solutions (South-West) Ltd | Bristol |
| Total Web Development | Greater Manchester |
| Total Web Solutions | Greater Manchester |
| Totality Services | |
| Totalize Media | |
| Totally Communications | Greater London |
| Totally Smart Homes Ltd | |
| TotallyMoney | |
| Totalscope IT Services Ltd | Lancashire |
| Totem Learning Ltd | |
| Toucan Computing Ltd | Greater London |
| Toucan Graphics | West Lothian |
| Toucan Internet, LLP | Essex |
| Touch Panel Products | Gloucestershire |
| Touch Screen Systems | Cambridgeshire |
| Touch-Base Ltd | Dorset |
| TouchFinder | |
| Touchlab Ltd | |
| Touchlight | |