| Digitec Systems Ltd | Oxfordshire |
| DigitilizeWeb | |
| Digition | |
| Digitizweb | |
| Digitla Guerrilla Consulting Ltd | |
| DigitLee | |
| Digitonic Ltd | |
| Digitopia | |
| Digitransformer Ltd | |
| Digitrol Ltd | Swansea |
| Digits Industries Ltd | Hampshire |
| DigitSense Ltd | |
| Digizone | |
| Diligence Digital | |
| Dimension Computer Services | Aberdeenshire |
| Dimension Studio | |
| Dimensional Imaging Ltd | |
| Dimensions AI | |
| Dimmock Web Marketing | Hertfordshire |
| Dinabite | |
| Dinamiks | West Sussex |
| Dino Media Ltd | Bristol |
| Dinonach | Oxfordshire |
| Diode | |
| Direct Data Systems | West Yorkshire |
| Direct Insight | Northamptonshire |
| Direct Pc Fix | Greater London |
| Direct Telecom Services | Cambridgeshire |
| Direct Voice and Data | West Yorkshire |
| Directions Ltd | Kent |
| Direk Ltd | |
| Dirlik Controls Ltd | Warwickshire |
| Dirty Martini Marketing | |
| DIS Solutions Ltd | |
| DISC Computer Repairs | |
| Disc Factory Ltd | Hampshire |
| Disc Makers UK | Hertfordshire |
| Discodog Ltd | Edinburgh |
| Discount Communications Ltd | County Durham |
| Discount Web Design | |
| Discountcomms | Surrey |
| DiscountDomains | |
| Discover IT | Berkshire |
| Discovery Agency Yorkshire Ltd | |
| Discovery Design | County Durham |
| Discovery Educational Software | Angus |
| Discus Group Ltd | Northamptonshire |
| Discus Systems plc | West Midlands |
| Disguise | |
| Disk Doctors Lab Ltd | |