| T-Systems Multimedia Solutions GmbH | Saxony |
| T. Wöhrle GmbH | Hamburg |
| T.S. Team-Software GmbH | North Rhine-Westphalia |
| T2 Software GmbH | |
| t2cure GmbH | |
| 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 |
| tailor-made software GmbH | |
| Taipan Investment GmbH | |
| TaKeTV GmbH | |
| Tako Deppe | Bremen |
| Tako e.K. | North Rhine-Westphalia |
| takomat Agentur GbR | North Rhine-Westphalia |
| Taktile GmbH | |
| Taktum Informatik GmbH | North Rhine-Westphalia |
| TAL.DE Klaus Internet Service GmbH | North Rhine-Westphalia |
| Tale About Data | |
| Taledo GmbH | |
| Talenteco GmbH | |
| Talentee | |
| TalentiMotion GmbH | Hesse |
| Talentry GmbH | Bavaria |
| TalentSpace GmbH | |
| Talicom GmbH | Lower Saxony |
| talk+ GmbH | |
| Talke Networks GmbH | |
| Talkline GmbH & Co. KG | Schleswig-Holstein |
| Tallence GmbH | Hamburg |
| Talon.One GmbH | |
| Talpasolutions GmbH | |
| Tampermonkey | |
| TamTech GmbH | |
| Tandler.com Gesellschaft für Umweltinformatik mbH | Bavaria |
| Tangany GmbH | |
| Tangerine-Software | Bavaria |
| Tankerkönig UG (haftungsberschränkt) | |
| Tanmar Webentwicklung | Berlin |
| Tanso Technologies GmbH | |
| TANTE PUH Onlineservice | Hesse |
| Tänzermedien GmbH | North Rhine-Westphalia |