| Corinium Global Intelligence | |
| Corintech Ltd | Hampshire |
| Corinthian Technical Solutions Co. Ltd | West Sussex |
| Cormica Ltd | |
| Cornelius-Electronics Ltd | Neath Port Talbot |
| Corner Pocket Ltd | Staffordshire |
| Corner Wearables Ltd | |
| Cornerstone Design and Marketing | |
| Cornerstone Oxford | |
| Cornerstone Venture Partners, LLP | |
| Cornish WebServices | Kent |
| Cornwall College | |
| Cornwall Development Company | |
| Coronet Services Ltd | |
| Corpdata Ltd | |
| Corporate Mobile Recycling Ltd | Greater London |
| Corporate Project Solutions | Buckinghamshire |
| Corporation Pop Ltd | |
| Corpteluk | Greater Manchester |
| Corre Data Systems Ltd | Essex |
| Correct Group | Greater London |
| CORRIN Software Products Ltd | Northamptonshire |
| Corsair Software | |
| Cortec IT Solutions Ltd | |
| Cortex Controllers Ltd | Cambridgeshire |
| Cortex Technology | |
| COSAC | Lisburn and Castlereagh |
| Cosdec Alpha | |
| CoSector | |
| Cosine | |
| CosmicSiteDesign.com | Bristol |
| Cosmient AI | |
| Cossack Labs Ltd | |
| CostaCode | |
| CoTech | |
| Cotswold Connection | Gloucestershire |
| Cotswold Web Services | Gloucestershire |
| Cottagewebs | |
| Cotton Mouton Diagnostics Ltd | |
| Cougar Automation | Hampshire |
| Count SEO UK | |
| Count Technologies Ltd | |
| Counter Solutions | Derbyshire |
| Counter-Act Systems | Buckinghamshire |
| Countersoft Ltd | |
| Counting Thoughts Ltd | Glasgow |
| Countly | Greater London |
| Courageous DS Ltd | |
| Coursedot | |
| Courtyard Electronics Ltd | Hampshire |