| ID | Name | Type |
|---|---|---|
| #2604 | Clive Townsend | + |
| #2605 | Clive Wilson | + |
| #2606 | Clizio Merli | ? |
| #2607 | Clockbyte | ? |
| #2608 | Clockwize Software Developments | Z |
| #23185 | Clockwork Robot | P |
| #2609 | Cloud 10 Software | Z |
| #2610 | Cloud 9 Software | Z |
| #2611 | Cloud Soft | Z |
| #2612 | Cloue | ? |
| #2613 | Clover Services | Z |
| #2614 | Clovis L. Tondo | ? |
| #2615 | Clown | ? |
| #23217 | Club Español Independiente de Usuarios de Sinclair QL | U |
| #2616 | Club Software | Z |
| #22769 | Club de Aventuras AD (CAAD) | P |
| #20247 | Clube Nacional de Aventura | P |
| #2617 | Clwyd Adventure Software | Z |
| #17143 | Clwyd Personal Computers | H |
| #2618 | Clyde W. Bish | + |