| TIGER Invest Oy | Transport & logistics | 2019 |
| TIIM Ilvesluoto Oy | Wholesale & retail | 2013 |
| Tilitoimisto Roi Tilikunto Ky | Professional & scientific | 2005 |
| TJ Nurmi Oy | Financial services | 2024 |
| TJA Konsultointi Oy | Professional & scientific | 2026 |
| TK-Sähkötekniikka Ky | Construction | 2011 |
| TM-Konex Oy | Wholesale & retail | 1997 |
| TMH Capital Oy | Professional & scientific | 2026 |
| TPM Consulting Oy | Professional & scientific | 2021 |
| TREEFORM Oy | Professional & scientific | 2011 |
| TT Verkosto Oy | Administrative & support | 2025 |
| TTJ Margeting Oy | Construction | 2007 |
| TVL - Taksit Oy | Transport & logistics | 2021 |
| TaKe Clean Avoin yhtiö | Administrative & support | 2005 |
| Tahsin Foundation Oy | Construction | 2024 |
| Tahsin Invest Oy | Construction | 1998 |
| Taidekehystämö Hyvärinen Oy | Manufacturing | 1980 |
| Taidevellamo Oy | Wholesale & retail | 2022 |
| Taiga Asunnot Oy | Real estate | 2025 |
| Taiga Capital Oy | Real estate | 2022 |
| Taiga Kiinteistöt OY | Construction | 2021 |
| Taiga Kodit Oy | Hospitality | 2014 |
| Taina Kerkelä Oy | Wholesale & retail | 2013 |
| Taitometsä Oy | Agriculture & fishing | 2025 |
| Taivaanalla Oy | Wholesale & retail | 2020 |
| Taksi Car Ola Oy | Transport & logistics | 2019 |
| Taksi Juotasniemi Oy | Transport & logistics | 2007 |
| Taksi Kontula Oy | Transport & logistics | 2022 |
| Taksi NikOja Oy | Transport & logistics | 2026 |
| Taksi T. Rinne Oy | Transport & logistics | 2018 |
| Taksi Vilén Oy | Transport & logistics | 2022 |
| Tallitontun Piha Oy | Administrative & support | 2009 |
| TaloTuki Rovaniemi Oy | Professional & scientific | 2007 |
| Taloasi Oy | Construction | 2015 |
| Talotekniikka Keskitalo Ky | Construction | 1999 |
| Talous-Aksa Oy | Professional & scientific | 1994 |
| Tamaroi Oy | Hospitality | 2023 |
| Tamates-Service Oy | Manufacturing | 1986 |
| Tamo-Steel Oy | Manufacturing | 1993 |
| Tang Ren avoin yhtiö | Hospitality | 2012 |
| Tanjan Kaupat Oy | Wholesale & retail | 2020 |
| Tapsan Grilli ja Kioski Tapio Viitala Ky | Wholesale & retail | 1988 |
| Tarja Karinen Oy | Health & social care | 2023 |
| TarjoaMinulle.fi Suomi Oy | Information & communication | 2015 |
| Tarkiainen Holding Oy | Real estate | 2014 |
| Tarttis Oy | Wholesale & retail | 1985 |
| Tarveosat Ky O. Keränen | | 1987 |
| Taste the North Oy | Hospitality | 2024 |
| Tatiana Beauty Oy | Other services | 2022 |
| Taxa Oy | Transport & logistics | 2018 |
| Taxiroad Oy | Transport & logistics | 2019 |
| Teemu Kinnunen Oy | Professional & scientific | 2016 |
| Tehdas-Asu, Olavi Tenhunen Oy | Wholesale & retail | 1979 |
| Tehes Oy | Wholesale & retail | 2023 |
| Tekee vain Oy | Other services | 2024 |
| Tekniikka ja Liikenne Repo Oy | Transport & logistics | 2019 |
| TeknoDesign Oy | Professional & scientific | 2023 |
| Tel-Rak Koponen Oy | Construction | 1995 |
| Telkkälän Vesiosuuskunta | Water & waste | 2002 |
| Tennispuiston Perustuki Oy | Professional & scientific | 1987 |
| Teotie Oy | Wholesale & retail | 1993 |
| Tepafix Oy | Other services | 2024 |
| Teppo Juotasniemi Oy | Construction | 2024 |
| Tepponeers Oy | Real estate | 2019 |
| Terapiapalvelu Mielen Avaimet Oy | Health & social care | 2026 |
| Terapiapalvelu Sirius Oy | Health & social care | 2022 |
| Tero Tornberg Oy | Construction | 2024 |
| Tero ja Mari Jolanki avoin yhtiö | Wholesale & retail | 2017 |
| Teräketjuhuolto Keski-Lappi Oy | Agriculture & fishing | 2023 |
| Tessat Oy | Information & communication | 2020 |
| Texmoda Oy | Wholesale & retail | 1993 |
| Thai-Luksua Oy | Hospitality | 2021 |
| Thatswhy Oy | Arts & recreation | 2023 |
| The Finnish Crêperie Oy | Hospitality | 2022 |
| The Four Seasons of Finland Oy | Wholesale & retail | 2021 |
| The Kampaamo Oy | Other services | 2019 |
| The Parturi Group Oy | Other services | 2014 |
| The Sievers Consulting Oy | Professional & scientific | 2021 |
| Third Culture Group Oy | Wholesale & retail | 2007 |
| Thousand Lakes Real Estate Oy | Real estate | 2021 |
| Thousand Lakes Software Oy | Information & communication | 2019 |
| ThrEEE Capital Oy | Financial services | 2024 |
| TiTaTu Oy | Arts & recreation | 2020 |
| TiTu Promotions Oy | Hospitality | 2023 |
| Tiako Oy | Professional & scientific | 2026 |
| Tieneliö Oy | Construction | 2011 |
| Tietolappi Oy | Wholesale & retail | 1993 |
| Tiimitalo Oy | Real estate | 2004 |
| Tili- ja konsultointipalvelu Lappishcon Ky | Professional & scientific | 1999 |
| Tili-Ollilat Oy | Professional & scientific | 1989 |
| Tiliduo Pirjo Uutela Ky | Professional & scientific | 2015 |
| Tilihallinto Anttila Oy | Professional & scientific | 2010 |
| Tilintarkastus Enbuske Oy | Professional & scientific | 1995 |
| Tilintarkastus Hyvärinen Oy | Professional & scientific | 2021 |
| Tilintarkastus Lauhava Oy | Professional & scientific | 2014 |
| Tilintarkastus Piila Oy | Professional & scientific | 2024 |
| Tilintarkastus Rovatili Ky | Professional & scientific | 1998 |
| Tilintarkastus Saranki Oy | Professional & scientific | 2011 |
| Tilipalvelu Kallatsa Oy | Professional & scientific | 2022 |
| Tilipalvelut Petrelius Oy | Professional & scientific | 2026 |