| Clausematch | Greater London |
| Claytex Services Ltd | Warwickshire |
| CLD | |
| Clean Digital Ltd | |
| Clean Energy Consultancy Ltd | |
| Cleantech Innovate | |
| Clear Books plc | Greater London |
| Clear Cloud Computing Services Ltd | Lincolnshire |
| Clear Design UK Ltd | Bristol |
| Clear Line Tech | East Sussex |
| Clear Software | |
| Clear Surgical | |
| Clear Surgical | |
| Clear Thinking (Software) Ltd | East Sussex |
| Clear Vision Systems | East Riding of Yorkshire |
| Clear Visual Communications Ltd | |
| Clear.Bank | Bristol |
| ClearBank Ltd | Greater London |
| Clearcare Solutions Ltd | |
| ClearDebit | |
| Cleardrop Ltd | Essex |
| ClearFibre Ltd | |
| clearFusion Digital | Cornwall |
| ClearLine Communications Ltd | |
| Clearsight Consulting | |
| Clearsite Ltd | Channel Islands |
| ClearSky Logic Ltd | |
| Cleartarn Ltd | |
| Cleartext Systems Cyber | |
| Cleartwo | |
| Clearwater IT Services | |
| Cledara Ltd | |
| CleerVu | Isle of Man |
| Cleo AI Ltd | |
| Clere Electronic Agents Ltd | Berkshire |
| Cleveland Circuits Ltd | North Yorkshire |
| Cleveland Technologies Group | North Yorkshire |
| Clever Cherry (Midlands) Ltd | West Midlands |
| Clever Computer Solutions Ltd | Derbyshire |
| Clever Computer Solutions Ltd | |
| Clever Software Group | Hampshire |
| Click Click Marketing Ltd | |
| Click Consult Ltd | Cheshire |
| Click Intelligence Ltd | |
| Click IT Services | West Yorkshire |
| CLICK Web Development | Hampshire |
| Click4Assistance | Essex |
| Clickcartpro | Berkshire |
| ClickInc.com | Isle of Man |
| ClickJump | |