| SystemHausPro EDV-Beratung GmbH | Baden-Württemberg |
| Systemmanagement Service & Konzepte GmbH | |
| Systempartner Hagen GmbH | North Rhine-Westphalia |
| Systempartner IT-Vertriebs GmbH & Co. KG | |
| Systems-Integration UG (haftungsbeschränkt) | North Rhine-Westphalia |
| Systemworks EDV GmbH | |
| Systerra Computer GmbH | Hesse |
| Systrade GmbH | Hesse |
| Systrail | Saarland |
| Sysways GmbH | Bavaria |
| syte GmbH | |
| Sytec Automation GmbH | Berlin |
| SyTech System Technologies Schuler GmbH | Baden-Württemberg |
| Syzygy Group | |
| SZ Organisation und Software | Bavaria |
| SZe Schneider & Zirr engineering GmbH | Saxony |
| T&A Systeme GmbH | |
| T&T Datentechnik GmbH | Brandenburg |
| T+I Technologie- und InnovationsConsult GmbH | Berlin |
| T-CURX GmbH | |
| T-DIS Thrymr Digital Insurance Solutions GmbH | |
| t-droste | Bavaria |
| T-Systems International GmbH | Hesse |
| T-Systems Multimedia Solutions GmbH | Saxony |
| T. Wöhrle GmbH | Hamburg |
| T.S. Team-Software GmbH | North Rhine-Westphalia |
| T2 Software GmbH | |
| t2cure GmbH | |
| T3 Premium | |
| T3Planet | |
| TABO - Embedded Systems GmbH & Co. KG | |
| Tabris | Baden-Württemberg |
| Tacalyx GmbH | |
| Tacterion GmbH | |
| Tacto Technology GmbH | |
| Tactonom | Bavaria |
| Tactron Elektronik GmbH & Co. KG | Bavaria |
| TAD Pharma GmbH | |
| Tado GmbH | |
| TAFEU GmbH | Rhineland-Palatinate |
| tagsolution e-systems GmbH | Rhineland-Palatinate |
| Taifun Software AG | Lower Saxony |
| Taiga | |
| Taikomedia | |
| tailor-made software GmbH | |
| Taipan Investment GmbH | |
| take it agency GmbH | |
| Take it_ | |
| TaKeTV GmbH | |
| Tako Deppe | Bremen |