| Concirrus Ltd | Greater London |
| Concise Consulting Ltd | Cumbria |
| Concise Technologies Ltd | Cheshire |
| ConCom Website Design Ltd | Cheshire |
| Concrete VC Partners | |
| Concurrent Design Group | |
| Concurrent Technologies | Essex |
| Condense Reality | |
| ConeX International Ltd | Essex |
| ConferenceNow | Oxfordshire |
| Conficio Product Design Ltd | |
| Confident I.T. Solutions Ltd | |
| Congenica Ltd | |
| Conigital | |
| Conjura | |
| Connect 2 Telecommunications | Oxfordshire |
| Connect 360 International Ltd | Hertfordshire |
| Connect Appointments | |
| Connect Communications Services Ltd | |
| Connect Computer Consultants Ltd | |
| Connect Earth | |
| Connect Software Solutions Ltd | |
| Connect Studio | |
| Connect Ventures | |
| Connect-Auto | |
| Connect2t | North Yorkshire |
| ConnectCo Ltd | |
| Connected Energy Ltd | |
| Connected Financial Solutions UK Ltd | |
| Connections Recruitment | |
| connective3 Ltd | |
| ConnectiveOne | |
| Connector Solutions Ltd | |
| Connex One | |
| Connexim Ltd | |
| Connexion Ltd | Berkshire |
| Connor Solutions Ltd | Tyne and Wear |
| Conosco Group Ltd | |
| Conquest Wildman Ltd | Bedfordshire |
| Consider IT Ltd | Edinburgh |
| Consider This Agency | |
| Consilience | |
| Consilient Health Ltd | |
| Consilium UK Ltd | Renfrewshire |
| Console Doctor Ltd | Tyne and Wear |
| Consoles and Gadgets | Glasgow |
| ConsoneAI Ltd | |
| ConstantDotCo Ltd | |
| Constellation.AI Ltd | Greater London |
| Construct | |