| Chinkin Design | Norfolk |
| Chip Financial Ltd | Greater London |
| ChipFlow | |
| Chits UK Ltd | Greater London |
| CHKS | |
| Chocolate Lime | |
| Choppity Ltd | |
| Chordata Ltd | |
| Chorus Global Ltd | Somerset |
| Chris Blunt | Devon |
| Chris Fickling Design | Nottinghamshire |
| Chris Lever SEO | |
| Chris Marten | |
| Christine Wilson | |
| Christopher Robinson | Cheshire |
| Chromacity Ltd | |
| ChromaTwist Ltd | |
| Chrome-Dome Design | Oxfordshire |
| Chronos Therapeutics | Oxfordshire |
| Chrysalis Digital Ltd | |
| Chrysalis Training Ltd | Surrey |
| CHS Networks Ltd | Kent |
| Chucklefish Games | |
| Chunk Ideas Ltd | Glasgow |
| Chunky Frog Design Ltd | |
| Church International Ltd | Kent |
| ChurchDesk | |
| Churchgate Computer Services | Suffolk |
| CiaoWeb | Swansea |
| CiberDirect | Greater Manchester |
| Cignon | Berkshire |
| Cimteq | Wrexham County Borough |
| CIP Merchant Capital | |
| Circad Design Ltd | Suffolk |
| Circadia Technologies Ltd | |
| Circle | Cardiff |
| Circle Cloud Ltd | |
| Circle Interactive | Bristol |
| Circle Square Ltd | Greater London |
| Circle.cloud | |
| Circlebox Creative Ltd | Greater Manchester |
| Circulor | |
| Cirdan | |
| Cirencester Computer Repairs Ltd | Gloucestershire |
| Cirrus Logistics Ltd | Hampshire |
| Cirrus Software | Buckinghamshire |
| CirrusHQ | West Lothian |
| Cisillion | Surrey |
| Citation Cyber Ltd | |
| Cite | |