| Daily Mail and General Trust plc | |
| Daisy Group Ltd | Lancashire |
| Daisy Wholesale Ltd | Lancashire |
| Dakota Digital | |
| Daktela | |
| Dala Technologies Ltd | |
| Dale Studios (Leicester) Ltd | Leicestershire |
| Daletech Electronics Ltd | West Yorkshire |
| Dalton Net Service Ltd | |
| DaltonTx | |
| Daly Design | Bridgend |
| Daly International Pty Ltd | Berkshire |
| Daly Systems Ltd | Leicestershire |
| Damia Group | Surrey |
| Damselfly Creative | Derbyshire |
| DaMtech IT Support | |
| Dan Ashton Websites | Dorset |
| Dan Dineen | Somerset |
| Dan King Digital | |
| Dan Lindop | Cheshire |
| Dan Tech Repairs | |
| Dan Temple | |
| Dancerace plc | Somerset |
| Daneswood | Devon |
| Dangerous Studio Ltd | |
| Danntec Computer Solutions | |
| Dantech Electronic Engineering | Essex |
| Dantech ID Mark | Cardiff |
| Dappros Ltd | |
| DAQ Solutions Ltd | South Yorkshire |
| Dark Blue | |
| Dark Blue Computer Services | |
| Dark Blue Therapeutics Ltd | |
| Dark Group Ltd | Hampshire |
| Darknet | |
| Darkside Design Ltd | |
| Darkstream Studios | Belfast |
| Darktrace Holdings Ltd | |
| Darlington College | |
| DarlingtonEMS | Greater Manchester |
| Darren Kandekore Full Stack Developer | |
| Darren Langley | West Midlands |
| Dart Computing | Devon |
| Dart-Digital | Somerset |
| Dartcom Systems Ltd | Devon |
| Darwin Consultants Ltd | |
| Data Bear | |
| Data Catalyst Ltd | |
| Data Centre Alliance | Berkshire |
| Data Centre Dynamics Ltd | Greater London |