| ID | Name | Type |
|---|---|---|
| #16643 | SimonSoft | Z |
| #13376 | Simone Majocchi | + |
| #13377 | Simple Company | Z |
| #18974 | Simple Soft | P |
| #13378 | Simplesoft | Z |
| #13379 | Simply Software | Z |
| #21389 | Simpson Software | Z |
| #13380 | Simsoft | Z |
| #13381 | Simtron | ? |
| #17703 | Sin-Com | S |
| #19841 | Sinc LAIR | - |
| #13382 | Sinc Masters Creative Group | Z |
| #13384 | Sinclair Browne Ltd | Z |
| #13385 | Sinclair Club | Z |
| #22292 | Sinclair Club Zlín | P |
| #17704 | Sinclair Computer Club | S |
| #13387 | Sinclair Learning Lab | Z |
| #17705 | Sinclair Owners Software Library | X |
| #19572 | Sinclair QL Preservation Project | Z |
| #13390 | Sinclair Research Ltd | P |