| TT Better Trading Oy | Professional & scientific | 2007 |
| TT Car Center Oy | Wholesale & retail | 2017 |
| TT Toivonen OY | Construction | 2023 |
| TT-SPV Finland 1 Oy | Real estate | 2025 |
| TT-Teippi Oy | Professional & scientific | 2018 |
| TTA asennus oy | Construction | 2025 |
| TTT Holding Oy | Financial services | 2023 |
| TTT Tilat Oy | Real estate | 2024 |
| Tvh-Invest OY | Financial services | 2013 |
| TWT Group Oy | Hospitality | 2024 |
| Taara mobility Oy | Manufacturing | 2022 |
| Tahokas Oy | Construction | 2002 |
| Taide- ja kulttuuriosuuskunta Vaste | Arts & recreation | 2016 |
| Taidepäiväkoti Launeen Satakieli Oy | Education | 2006 |
| Taiga Lures Oy | Manufacturing | 2011 |
| Taikaliemi Oy | Hospitality | 2020 |
| Taimi Platform Oy | Information & communication | 2025 |
| Taiteviiva Oy | Professional & scientific | 2024 |
| Taitokax Oy | Real estate | 2021 |
| Taivasalla Oy | Professional & scientific | 1996 |
| Taivaskulta Oy | Wholesale & retail | 2021 |
| Takamäki Service Oy | Administrative & support | 2023 |
| Takasuoramainonta Ky | Professional & scientific | 2017 |
| Takkahuone Lahti Oy | Construction | 2020 |
| Takoja Development Oy | Real estate | 2023 |
| Taksi Juutilainen Ky | Transport & logistics | 2014 |
| Taksi Nurmi Oy | Transport & logistics | 2018 |
| Taksi Wallin Oy | Transport & logistics | 2015 |
| Taksipalvelu Lahti Oy | Transport & logistics | 2020 |
| Taksipalvelut Vanhanen Oy | Transport & logistics | 2018 |
| Talep Brothers Oy | Wholesale & retail | 2023 |
| Talo ja Rata Sähkö TRS Ky | Construction | 2011 |
| Talomen Oy | Construction | 2007 |
| Talotek Sähkö Oy | Construction | 2025 |
| Talotekniikka Purik Oy | Construction | 2023 |
| Talouden Vartija Ky | Professional & scientific | 2017 |
| Taloushallinto TeMe Oy | Professional & scientific | 2022 |
| Talouskaveri Oy | Professional & scientific | 2026 |
| Talovalvoja Oy | Construction | 2022 |
| Talverio Oy | Information & communication | 2026 |
| Talwood Oy | Manufacturing | 2022 |
| Tamka Group Oy | Professional & scientific | 2023 |
| Tammi-Palvelut Oy | Wholesale & retail | 2025 |
| Tammi-Tuote Ky | Manufacturing | 1974 |
| Tammikilpi Oy | Administrative & support | 2014 |
| Tamtron Precision Oy | Manufacturing | 1992 |
| Tangokellari Oy | Education | 2023 |
| Tanhula Yhtiöt Oy | Real estate | 2020 |
| Taoyuan Oy | Hospitality | 2026 |
| Tapahtuma Kimi Oy | Administrative & support | 2016 |
| Tapanila Equity Oy | Financial services | 2020 |
| Tapanilan Kartanokodit Oy | Real estate | 2019 |
| Tapio Anttila Collection Oy | Manufacturing | 2021 |
| Tapsaco Ky | Professional & scientific | 2013 |
| Tapuntassu Holdings Oy | Financial services | 2026 |
| TarSam Oy | Health & social care | 2023 |
| Tarkil Oy | Wholesale & retail | 1993 |
| Tarkka Isännöinti Oy | Real estate | 2023 |
| TarkkaJää Oy | Arts & recreation | 2025 |
| Tartex-Tuote Ky | Manufacturing | 1990 |
| Tasoite,maalaus ja rappaus taivaanranta oy | Construction | 2023 |
| Tasokas Software Oy | Information & communication | 2017 |
| Tasolaiset Lahti Oy | Administrative & support | 2025 |
| Tasotalo Oy | Real estate | 2020 |
| Tassuillen Oy | Wholesale & retail | 2013 |
| Taustatekijä Oy | Professional & scientific | 2001 |
| Tavarataksi Finland Oy | Transport & logistics | 1954 |
| Tavoitevaikuttaja-Ta-Va Oy | Professional & scientific | 1990 |
| Taxi KiPi Oy | Transport & logistics | 2017 |
| Taxipalvelu H. & T. Mikkonen Oy | Transport & logistics | 2024 |
| Taxrok Oy | Transport & logistics | 2009 |
| Tea Hagstedt Oy | Professional & scientific | 2016 |
| Team Gustafsson Oy | Health & social care | 2013 |
| Team Kaijasilta Oy | Health & social care | 2011 |
| Team Kiinteistöt Oy | Real estate | 2005 |
| Team Lehtimäki Oy | Arts & recreation | 2021 |
| Technology of Young Oy | Wholesale & retail | 2017 |
| TeePaja Oy | Hospitality | 2025 |
| Teemu Kirjonen Oy | Real estate | 2020 |
| Teemu Pöystilän Työllistämis Toimisto Oy | Construction | 2022 |
| Teemu Trading Oy | Financial services | 2020 |
| Teeren Cafe Oy | Hospitality | 2016 |
| Teerenpeli Hospitality Oy | Wholesale & retail | 2024 |
| Teerenpeli Panimo & Tislaamo Oy | Manufacturing | 2012 |
| Teerenpeli Ravintolat Oy | Hospitality | 1997 |
| Teerenpeli Yhtiöt Oy | Hospitality | 1994 |
| Tehotila Oy | Real estate | 1995 |
| Tehotoiminelikko Oy | Administrative & support | 2009 |
| Teippiklubi Oy | Wholesale & retail | 2018 |
| Teippimankeli Oy | Professional & scientific | 2022 |
| Tekesler Oy | Hospitality | 2015 |
| Tekeväiset Oy | Administrative & support | 2021 |
| Tekija AI Oy | Professional & scientific | 2025 |
| Tekninen Palvelu Tomi Niemi Oy | Professional & scientific | 2018 |
| Teknoware Emergency Lighting Oy | Manufacturing | 2022 |
| Teknoware Oy | Manufacturing | 1972 |
| Teknoware Rail&Road Oy | Manufacturing | 2025 |
| Tekstiili Hollotar, Liisa Ropponen Ky | Wholesale & retail | 1990 |
| Tekstiilisuunnittelutoimisto Kotitakki Oy | Professional & scientific | 2010 |
| Telivaunu Oy Weckman | Manufacturing | 1981 |