| Cohort Computers Ltd | Dorset |
| Cohort Studios Ltd | |
| Coinque Consulting | |
| Colbek Systems Ltd | Warwickshire |
| Colchester Web Design | Essex |
| Colcom Ltd | |
| Coldharbour | |
| Cole AD | |
| Coleg Sir Gâr | |
| Coleg y Cymoedd | |
| Coleswood Media | |
| Colewood Internet Ltd | County Durham |
| Colinton Website Design | Edinburgh |
| Coljam Consultants Ltd | Perth and Kinross |
| Collabco Ltd | |
| Collabit Software Ltd | |
| Collabor8online | |
| Collabora Ltd | |
| Collabora Productivity Ltd | Cambridgeshire |
| Collaborative Computational Project No. 4 | Oxfordshire |
| Collaborative Connections | West Sussex |
| Collate Business Systems Ltd | Hampshire |
| Collctiv Ltd | |
| Colleague Software Ltd | Norfolk |
| Collective Solutions Group | |
| Colleges Scotland | |
| Collegia | |
| Collidr Technologies Ltd | |
| Collision Management Systems Ltd | |
| Colmworth Electronics Ltd | Cambridgeshire |
| Colorintech | |
| Colortrac Ltd | Cambridgeshire |
| Colour Rich | |
| Colourways | |
| Colt Technology Services Group Ltd | |
| Columbus Telecom Ltd | Glasgow |
| Colva Ltd | |
| Colvill Banks Ltd | Hampshire |
| Colza | Greater London |
| Com5 | Hampshire |
| Combine Studio | South Yorkshire |
| Combine.ai | |
| Comcare Technology Ltd | Cheshire |
| Comcen Computer Supplies Ltd | Swansea |
| Comfort Click Ltd | |
| Comgem Ltd | Bridgend |
| Comgen | Bedfordshire |
| CoMind Technologies Ltd | |
| Comino Holding Ltd | |
| Comloc Computer Security | Greater Manchester |