| Cross-Check Systems Ltd | Warwickshire |
| Crossflow Payment Solutions Trading Ltd | |
| CrossTech | |
| Crossware Products | Hertfordshire |
| Croud | |
| Crover Ltd | |
| Crow Design | |
| Crowd Data Systems Ltd | |
| Crowd Technologies Ltd | West Midlands |
| Crowdcube Capital Ltd | Greater London |
| Crowdform | |
| Crowdfunder Ltd | |
| Crowdskills Ltd | |
| Crowdskills Ltd | |
| CrowdVision | Greater London |
| Crowers Ltd | |
| Crown Hosting Data Centres Ltd | |
| Croydon College | |
| Crozdesk Ltd | Greater London |
| CRS | |
| CRS Norwich | |
| CRS Technical Services | |
| CRU Technologies Ltd | |
| Crucial Software Ltd | Surrey |
| Crucial Web | |
| Crucible | |
| Cruise Technologies | |
| Crunch | |
| Crusade Computer Solutions Ltd | Staffordshire |
| Crusader AV | Nottinghamshire |
| Crush Digital | |
| Crush Pixels | |
| Crymbo | |
| Crymbo Ltd | |
| Cryoniss | |
| Crypta Labs Ltd | |
| Crypto Developers Ltd | |
| Crypton Computers Ltd | West Sussex |
| Crystal Digital Media | |
| Crystal Electronics Ltd | |
| Crystal Interactive | |
| Crystal Presentations Ltd | |
| Crystal radio systems ltd | Worcestershire |
| CrystalMaker Software Ltd | Oxfordshire |
| CrystecPharma | |
| CS Genetics Ltd | |
| CS Genetics Ltd | |
| CS One Designers | Kent |
| CS Systems | Greater Manchester |
| CSD Ltd | Northamptonshire |