| Camion Infrastructure Ltd | |
| Camis Electronics | West Midlands |
| Cammax Ltd | West Yorkshire |
| CamNtech Ltd | |
| Campaign Master (UK) Ltd | Greater London |
| Campbell Software Solutions Ltd | |
| CAMRADATA | |
| Camsat Ltd | |
| 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 | |
| CanCertain Ltd | |
| CANDDi | Greater Manchester |
| Candela Capital Ltd | North Yorkshire |
| Candela Consulting | |
| Candidsky | |
| Candour | |
| Candy Capital | Greater London |
| Candy Marketing | |
| Cannon Technologies Ltd | |
| Cannon Tomlinson Mansley Ltd | Cambridgeshire |
| Canny Creative | |
| Canon Medical Research Europe Ltd | Edinburgh |
| 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 |
| Cantillion King | |
| Cantura Ltd | Hertfordshire |
| Canute, LLP | West Yorkshire |
| CaoSys Ltd | West Yorkshire |
| CapametriX | |
| Capcom | Hampshire |
| Capita plc | |
| Capital Calibration Services Ltd | Greater London |
| Capital City College | |
| Capital Document Solutions | |
| Capital Economics Ltd | |
| Capital Enterprise (UK) Ltd | Greater London |
| Capital for Colleagues plc | |
| Capital Gains Ltd | |
| Capital Guards UK Ltd | Greater London |
| Capital Network Solutions | |