| Tanssikoulu Wimma Oy | Education | 2017 |
| Tapahtumalaite Oy | Wholesale & retail | 2015 |
| Tarja Pinta Oy | Health & social care | 2015 |
| Tarkka-ampujan Sarastus Oy | Energy | 2024 |
| Tarkkatassu Oy | Other services | 2025 |
| Tarranalle Oy | Manufacturing | 2023 |
| Tasa Invest Oy | Real estate | 2015 |
| Tasac-Markkinointi Ky | Wholesale & retail | 1992 |
| Tasim Oy | Wholesale & retail | 2019 |
| TaskBrain Oy | Information & communication | 2025 |
| Tasoi Design Oy | Construction | 2021 |
| Tavira Oy | Wholesale & retail | 2005 |
| Teatteri Hysteria Oy | Arts & recreation | 2019 |
| Techter It Oy | Health & social care | 2021 |
| Tehokat Oy | Construction | 1992 |
| Tekijänhallit Oy | Real estate | 2021 |
| Teknim Oy | Manufacturing | 2018 |
| Teknopolar Oy | Real estate | 1990 |
| Tekstiili Mannermaa Oy | Wholesale & retail | 1986 |
| Telemarkki Kiinteistöt Oy | Real estate | 2020 |
| Telog Oy | Construction | 2010 |
| Temacon Finland Oy | Construction | 2007 |
| Temcol Oy | Real estate | 1990 |
| Tenho Yhtiöt Oy | Administrative & support | 2008 |
| Teollisuusasennus Valtasaari Oy | Manufacturing | 2017 |
| Tepeka Oy | Financial services | 2021 |
| TerapiaTaivas Oy | Health & social care | 2015 |
| Terveyskauppa Reetta Ky | Wholesale & retail | 2005 |
| Terveysteko Oy | Health & social care | 1986 |
| The Art Neon Oy | Professional & scientific | 2022 |
| The Jaakko Oy | Financial services | 2021 |
| The Olive Lounge Oy | Hospitality | 2023 |
| Thermal Management Group Oy | Professional & scientific | 2022 |
| Thermal Management Oy | Manufacturing | 2023 |
| ThermoHaus -pro Oy | Construction | 1994 |
| TiLOI Oy | Real estate | 2018 |
| Tieliikennekoulutus MIKRA Ky | Education | 2014 |
| Tifomo Oy | Transport & logistics | 2008 |
| Tiisakki Oy | Construction | 2022 |
| Tikkala Service Oy | Construction | 2010 |
| Tilatalo Oy | Construction | 1980 |
| Tilausliikenne Kaataja Oy | Transport & logistics | 2008 |
| Tilausliikenne Kivimäki Oy | Transport & logistics | 1997 |
| Tili Art-Tec Oy | Professional & scientific | 2004 |
| Tili-Joensuu Oy | Professional & scientific | 1995 |
| TiliSaukko Oy | Professional & scientific | 2020 |
| Tilikki Yrityspalvelut Oy | Professional & scientific | 2022 |
| Tilineuvonta Hietakangas Oy | Professional & scientific | 2021 |
| Tilintarkastus Brikka Oy | Professional & scientific | 2023 |
| Tilintarkastus Helena Takala Oy | Professional & scientific | 2013 |
| Tilintarkastus Leppäniemi Oy | Professional & scientific | 2024 |
| Tilintarkastus M&K Oy | Professional & scientific | 2022 |
| Tilintarkastus Mikko Sillanpää Oy | Professional & scientific | 2018 |
| Tilintarkastus Mäkelä Oy | Professional & scientific | 2018 |
| Tilintarkastus Samuel Niemelä Oy | Professional & scientific | 2025 |
| Tilipalvelu Tasia avoin yhtiö | Professional & scientific | 2017 |
| Tilitoimisto Haukkala Oy | Professional & scientific | 1973 |
| Tilitoimisto Jokinen Oy | Professional & scientific | 1994 |
| Tilitoimisto L. Hyvönen Ky | Professional & scientific | 1983 |
| Tilitoimisto Luokkamäki Ky | Professional & scientific | 1985 |
| Time2Move Oy | Education | 2014 |
| Timintra Consulting Oy | Professional & scientific | 1997 |
| Timo Marttila Avoin Yhtiö | Manufacturing | 1992 |
| Timo Tapio Kallio Ky | Wholesale & retail | 1999 |
| Tinttala Oy | Real estate | 1984 |
| Tiskari Oy | Wholesale & retail | 2004 |
| Tkekalainen Oy | Health & social care | 2025 |
| Tohina Varhaiskasvatus Oy | Education | 2019 |
| Toimintojen Tori Oy | Real estate | 2002 |
| Tomanopi Oy | Administrative & support | 2017 |
| Tommi Palomäki Ky | Wholesale & retail | 1998 |
| Toni Rajamäki Consulting Oy | Professional & scientific | 2025 |
| Tonttukoti Oy | Real estate | 1993 |
| Top Sound Oy | Wholesale & retail | 1981 |
| Topakka Yrityspalvelu Ky | Professional & scientific | 2013 |
| Topin Auto Oy | Wholesale & retail | 2016 |
| Toppari Kiinteistöt Oy | Real estate | 1995 |
| Trailander Oy | Manufacturing | 1999 |
| Train Factory Parking Oy | Real estate | 2022 |
| TrainIT Pro Oy | Education | 2023 |
| Traktorihuolto Esa Heikkilä kommandiittiyhtiö | Real estate | 1983 |
| Trans Haapala Ky | Transport & logistics | 2017 |
| Tres Amigos Capital Oy | Real estate | 2015 |
| Trestec Oy | Professional & scientific | 1983 |
| Triest Invest Oy | Financial services | 2016 |
| Triforma Oy | Professional & scientific | 1991 |
| Tripod Immaterial Oy | Administrative & support | 2026 |
| Trivante Oy | Financial services | 2025 |
| Troxia Solutions Oy | Information & communication | 1994 |
| Troya Group Oy | Wholesale & retail | 2024 |
| Trutec Holding Oy | Financial services | 2020 |
| Trutec Oy | Construction | 2008 |
| Tukipalvelut Kyy Oy | Real estate | 2018 |
| Tukkusein Oy | Wholesale & retail | 1993 |
| Tukkutalo Heinonen Oy | Wholesale & retail | 1992 |
| Tulituote Oy | Wholesale & retail | 2008 |
| Tunnelmatalo Oy | Hospitality | 2026 |
| Tunnepaja Oy | Health & social care | 2024 |
| Tuohirulla Oy | Financial services | 2026 |
| Tuomikylän Asennus Ky | Manufacturing | 1988 |