| Comm Store Ltd | Norfolk |
| Comm-Tech | |
| Comm-Tech Martham Ltd | Norfolk |
| Comma Payments Ltd | |
| CommAgility Ltd | Leicestershire |
| Commatic | Gloucestershire |
| Commerce Business Automation | |
| Commerce Centric | Berkshire |
| CommerceTuned | Hertfordshire |
| Commerceworks Technology Ltd | |
| Commercial Ltd | Gloucestershire |
| Commercial Space Technologies Ltd | |
| Commissum | Edinburgh |
| Commlinks | Greater London |
| Common Ground | Oxfordshire |
| Common Knowledge | |
| Common VC | Greater London |
| Common Works | |
| Commonplace | |
| Commonwealth Telecommunications Organisation | Greater London |
| Comms Consultants | Cheshire |
| Comms Express Ltd | Essex |
| Comms Group (UK) Ltd | Northamptonshire |
| Comms.UK Ltd | Dorset |
| CommsFM Ltd | Glasgow |
| Commsplus Ltd | Somerset |
| Commsupport Networks Ltd | |
| Commsworld Ltd | Edinburgh |
| Commtech2000 UK Ltd | Greater Manchester |
| Communere | |
| Communication Design Partnership | |
| Communications Advisory Service | Berkshire |
| Communications and Utilities Regulatory Authority | |
| Communications Audit UK Ltd | Gloucestershire |
| Communications Solutions UK | Berkshire |
| Communion Saves Ltd | |
| Communisis Ltd | |
| Communiti | |
| Community Fibre Ltd | Greater London |
| Community Sites | East Sussex |
| Community Ventures Partnerships Ltd | |
| Community Web Initiative | |
| Commusoft Ltd | |
| CommVersion UK Ltd | Greater London |
| Commvia | Tyne and Wear |
| Company Net Ltd | Edinburgh |
| Compare the Cloud Ltd | |
| Comparesoft | |
| Comparitech Ltd | |
| Compass Computing Ltd | Devon |