| CUR8 | |
| Curator+Co Ltd | |
| Curileum Discovery | |
| Curly Creative | Hampshire |
| CurrantWeb | West Midlands |
| Currencies Direct | |
| Currency.com | Gibraltar |
| Currencycloud | Greater London |
| Currensea Ltd | |
| Currer Web | Gloucestershire |
| Cursive | |
| Cursor Insight | |
| Curve Games | |
| Curve Information Technology Ltd | East Sussex |
| Curve OS Ltd | Greater London |
| Curve Therapeutics | |
| Curve UK Ltd | Greater London |
| Curvestone AI | |
| Cushon Group Ltd | |
| Cuskit Ltd | Staffordshire |
| Custard Online Marketing Ltd | Greater Manchester |
| Custardfish Web Design | Suffolk |
| Custom Computer Services Wales Ltd | Cardiff |
| Custom Creative Solutions Ltd | |
| Custom Database Design | Greater Manchester |
| Custom Interconnect Ltd | Hampshire |
| Custom Internet Ltd | Hampshire |
| Custom Micros | West Yorkshire |
| Custom Networks Ltd | Surrey |
| Custom Pharma Services | |
| Custom Software Systems | Renfrewshire |
| Custom Transformers Ltd | Wiltshire |
| Customer Systems plc | Surrey |
| Customer360 | |
| CustomerOS | |
| CustomerSure | |
| Cutec Ltd | Devon |
| Cutting Edge Projects Ltd | |
| Cutting Edge Software | Essex |
| Cuttlefish Multimedia Ltd | Leicestershire |
| CVW Web Design | West Sussex |
| CWL Systems | |
| CWS Software | |
| Cyacomb Ltd | |
| Cyan Technology Ltd | Cambridgeshire |
| Cyanetics Ltd | |
| Cyangold Ltd | Greater London |
| Cybake Ltd | |
| Cybase | Merseyside |
| Cyber | Hertfordshire |