| Certo Software Ltd | |
| Certum Ltd | Glasgow |
| Certus Technology | |
| Cervest | Greater London |
| Cestrian | Greater Manchester |
| CETA Software Ltd | Oxfordshire |
| Cetix Ltd | Aberdeen |
| Cetronic Power Solutions Ltd | Hertfordshire |
| Cezanne HR Ltd | |
| CF Systems | |
| CFH Docmail Ltd | Somerset |
| CFP Ltd | Derbyshire |
| CFP Software Ltd | Cornwall |
| CG Design | Lancashire |
| CG Hero Ltd | |
| CGL Systems | |
| CH Digital | Staffordshire |
| Chadwick Design Ltd | Lincolnshire |
| Chagency | |
| CHAIN Biotechnology Ltd | |
| Chalfont Web Design | Buckinghamshire |
| Chalvington Communications Ltd | East Sussex |
| Chameleon Studios Ltd | Cambridgeshire |
| Chameleon Technology (UK) Ltd | |
| Chameleon Web Services Ltd | |
| Chameloeon Media | Hampshire |
| Changingday Ltd | |
| Channel 3 Consulting | |
| Channel Communication Services Ltd | Bristol |
| Channel Digital Ltd | Cornwall |
| ChannelDoubler | Greater London |
| Chant 4 | Nottinghamshire |
| Chaos | Surrey |
| Chapman Hamer Ltd | Worcestershire |
| Chaptr | Hampshire |
| char.gy Ltd | |
| Charco Neurotech | |
| Charcroft Electronics Ltd | Powys |
| ChargedEV | |
| Chargepoint Technology Ltd | |
| Charisma | |
| Charles Square | |
| Charlton Networks | Gloucestershire |
| CHARM Therapeutics | |
| Charnwood Discovery | Leicestershire |
| Charnwood Molecular | |
| Charter Savings Bank | West Midlands |
| Chartered Developments | |
| Chartus Ltd | Gloucestershire |
| Chartwell-Yorke Ltd | Greater Manchester |