| DCUK | |
| DDC Engineering Solutions Ltd | |
| DDI Software | |
| DDME Ltd | West Yorkshire |
| DDS Web Design | |
| De Facto | Nottinghamshire |
| De Facto Software Ltd | Suffolk |
| De Montfort University | Leicestershire |
| De Rossi Consulting Ltd | |
| Dead Simple Computing | |
| DeadHappy | |
| Deadly Byte Ltd | |
| Deal Lite | |
| Dealerweb | |
| Deans Computer Services plc | West Yorkshire |
| Deazy | Bristol |
| DebugBear Ltd | |
| Debut | Greater London |
| debutWEB | |
| Decade Monitoring Solutions Ltd | West Midlands |
| Decent Group | Wiltshire |
| Decide | |
| Decision Systems Ltd | Greater Manchester |
| Decision Technologies | |
| Deciwatt Ltd | |
| Deckchair | Bristol |
| Decodifi | |
| Decorte Future Industries Ltd | |
| Dedicatech Ltd | |
| Dedicated Partnership Ltd | |
| Deeho Ltd | Bedfordshire |
| Deep Blue Logic | Devon |
| Deep Blue Systems Ltd | Buckinghamshire |
| Deep Design | Isle of Wight |
| Deep Footprints Web Design & Development | |
| Deep Render | Greater London |
| Deep Science Ventures | |
| Deep Science Ventures | |
| Deepblue Digital (Leeds) Ltd | West Yorkshire |
| Deepcytes | |
| Deepdale | North Yorkshire |
| DeeperThanBlue | |
| DeepInspire | |
| Deeply Digital | |
| Deepmatter Group Ltd | |
| DeepRender | |
| DeepStream Technologies Ltd | Greater London |
| Deeptech Labs | Cambridgeshire |
| Deepvault Internet Services | Powys |
| Deerfoot IT Resources Ltd | Hampshire |