| Cambridge Science Park | Cambridgeshire |
| Cambridge Technology Consultants Ltd | Cambridgeshire |
| Cambridge Touch Technologies Ltd | Cambridgeshire |
| Cambridge Web Marketing Co. | Cambridgeshire |
| Cambridge Wireless | Cambridgeshire |
| Cambron Software Ltd | |
| Cambs Digital | |
| Cambs Web Design | |
| Camena Bioscience | |
| Cameron Wells | |
| CamGraPhIC Ltd | |
| Camis Electronics | West Midlands |
| Cammax Ltd | West Yorkshire |
| CamNtech Ltd | |
| Campaign Master (UK) Ltd | |
| Campbell Software Solutions Ltd | |
| CAMRADATA | |
| Camtech Systems Ltd | Cambridgeshire |
| Can Studios Ltd | South Yorkshire |
| Canaree | |
| Canary Dwarf | Moray Council |
| Canary Wharf Laptop Repairs | |
| Cancer Research UK Cambridge Institute | |
| Cancer Research UK Scotland Institute | |
| CANDDi | Greater Manchester |
| Candela Capital Ltd | North Yorkshire |
| Candela Consulting | |
| Candy Capital | Greater London |
| Cannon Technologies Ltd | |
| Cannon Tomlinson Mansley Ltd | Cambridgeshire |
| Canon Medical Research Europe Ltd | |
| Canon UK | Surrey |
| Canonical Ltd | |
| CanSense Ltd | |
| Cantab Software Ltd | Cambridgeshire |
| Canterbury Christ Church University | Kent |
| Canterbury Christ Church University - Computer Science and Technology | Kent |
| Canterbury Web Services Ltd | Kent |
| Cantura Ltd | Hertfordshire |
| Canute, LLP | West Yorkshire |
| CaoSys Ltd | West Yorkshire |
| Capcom | Hampshire |
| Capita plc | |
| Capita plc | |
| Capital Calibration Services Ltd | Greater London |
| Capital City College | |
| Capital Document Solutions | |
| Capital Economics Ltd | |
| Capital Enterprise (UK) Ltd | |
| Capital Enterprise (UK) Ltd | |