| Treuhand Oy | Real estate | 2022 |
| Triadi Office Oy | Wholesale & retail | 2003 |
| Triokem Oy | Wholesale & retail | 2024 |
| Trust Partners Oy | Professional & scientific | 1990 |
| Tuias Oy | Manufacturing | 2025 |
| Tuiskuluoto Oy | Transport & logistics | 2010 |
| Tule Pesulle oy | Other services | 2025 |
| Tulkkauspalvelu Hei vaan Oy | Professional & scientific | 2024 |
| Tulosraha Oy | Construction | 1987 |
| Tunneopas Oy | Health & social care | 2026 |
| Tunturipuun Kauppa Oy | Wholesale & retail | 2025 |
| Tuohitek Oy | Manufacturing | 2016 |
| Tuomas Autio Oy | Wholesale & retail | 2002 |
| Tuomo Ala-Anttila Ky | Construction | 2006 |
| Tupla-Woltti Oy | Construction | 1993 |
| TurvaPioneerit Oy | Construction | 2024 |
| Turvavyö Oy | Wholesale & retail | 1971 |
| Tuulin Terveys Oy | Health & social care | 2006 |
| Tyni Group Oy | Real estate | 2017 |
| Tyrni Invest Oy | Financial services | 2021 |
| Työ-Rukkanen Oy | Other services | 2020 |
| Työpsykologia Mikko Pohjola Oy | Health & social care | 2026 |
| Työvoitto Oy | Administrative & support | 2021 |
| TÄYSII Oy | Arts & recreation | 2018 |
| Törmätek Oy | Administrative & support | 2023 |
| U4 Rakennus Oy | Construction | 2020 |
| UKT, Uudenmaan Kiinteistötarkastus Oy | Professional & scientific | 2021 |
| UPU Pohjarakennus Ky | Construction | 2005 |
| Urakointi Kontiainen OY | Construction | 2008 |
| Ulkoinen Tahdistin Oy | Information & communication | 2008 |
| Umppis Oy | Wholesale & retail | 2025 |
| UnelmaTupa LKV Oy | Real estate | 2010 |
| Unelmatiimi Oy | Arts & recreation | 2016 |
| Uniquno Oy | Professional & scientific | 2022 |
| Unja Songs Oy | Wholesale & retail | 2006 |
| Urakointi M.Hupponen Oy | Administrative & support | 2023 |
| Uras Oy | Wholesale & retail | 2021 |
| Urheilu-Alho Oy | Wholesale & retail | 1996 |
| Urheilun Uutistuotanto UT Oy | Information & communication | 1992 |
| Urheilutalo ja kesävirkistys Oy | Financial services | 1932 |
| Ursviken Investment Oy | Financial services | 2012 |
| Usmin Fysioterapiapalvelu Oy | Wholesale & retail | 1995 |
| Uudenmaan ATK-tietokonetuki Oy | Information & communication | 2011 |
| Uudenmaan Energiamyynti Oy | Wholesale & retail | 2013 |
| Uudenmaan Farmipalvelu Ky | Wholesale & retail | 1988 |
| Uudenmaan Hissipojat Oy | Professional & scientific | 1990 |
| Uudenmaan Kaivin Oy | Construction | 1992 |
| Uudenmaan LVI-TaloTekniikka Oy | Construction | 2024 |
| Uudenmaan Laaturakennus Oy | Construction | 2015 |
| Uudenmaan Nuohouspalvelu Oy | Administrative & support | 2014 |
| Uudenmaan Palveluohjaus avoin yhtiö | Health & social care | 2007 |
| Uudenmaan Piha & Kivi Oy | Administrative & support | 2022 |
| Uudenmaan Rakennemestarit Oy | Professional & scientific | 2008 |
| Uudenmaan Remonttiapu Oy | Construction | 2013 |
| Uudenmaan Seuramatkat Oy | Administrative & support | 1968 |
| Uudenmaan Sähkärit Oy | Construction | 2020 |
| Uudenmaan Tili- ja toimistoapu Oy | Administrative & support | 1996 |
| Uudenmaan Timanttisahaus ja -poraus Oy | Construction | 1989 |
| Uudenmaan Tukipalvelut Oy | Professional & scientific | 1999 |
| Uudenmaan Yritysapu Oy | Professional & scientific | 2019 |
| Uudenmaan kiinteistökunnostus oy | Construction | 1996 |
| Uudenmaan koirahoitola Oy | Other services | 2023 |
| Uudenmaan koirakylpylä Oy | Other services | 2024 |
| Uudenmaan sijoituspalvelu Oy | Financial services | 2008 |
| Uusin Tuulin Oy | Professional & scientific | 2017 |
| Uustai Oy | Real estate | 1989 |
| Viiden Tähden Taksit OY | Transport & logistics | 2018 |
| Villimimmi OY | Other services | 1997 |
| Vip Remontit Ky | Wholesale & retail | 1996 |
| Vipox OY | Construction | 2026 |
| VIS Suomen Kiskokalustotehdas Oy | Manufacturing | 2024 |
| VJH Rakennuspalvelu Oy | Construction | 2015 |
| VLN Business Oy | Wholesale & retail | 2026 |
| VMS Invest Oy | Wholesale & retail | 2013 |
| VMT Foods Oy | Wholesale & retail | 2017 |
| VN Urakointi Oy | Construction | 2026 |
| VP Vuokra Oy | Administrative & support | 2024 |
| VPJ Consulting Oy | Administrative & support | 2026 |
| VPP Palvelut Oy | Professional & scientific | 2020 |
| VT Group Oy | Professional & scientific | 1990 |
| VT-Palvelut Oy | Professional & scientific | 2012 |
| Vaahteramäki Invest Oy | Financial services | 2024 |
| Vah-Vis Oy | Financial services | 1989 |
| Vaherco Oy | Financial services | 1985 |
| Vahvelainen Oy | Administrative & support | 1987 |
| Vain10 Oy | Arts & recreation | 2007 |
| Vair KPK osk. | Construction | 2010 |
| Vaisaton Oy | Other services | 2021 |
| Vaiveronkadunkioski Oy | Wholesale & retail | 1988 |
| Valdan Nordic Oy | Wholesale & retail | 2021 |
| Valli-Sähkö Ky | Construction | 1992 |
| Vallilan Merkki ja Tavara Oy | Information & communication | 2022 |
| Valoicon Oy | Construction | 1992 |
| Valoisa Polku Oy | Other services | 2021 |
| Valueqon Oy | Professional & scientific | 2024 |
| Vamox Oy | Information & communication | 2024 |
| Vaneri Team Ky | Manufacturing | 1990 |
| Vanhusten kotipalvelu Elina Kokkonen Ky | Health & social care | 2006 |
| VarCons Oy | Professional & scientific | 2015 |
| Varaosamarkkinat Salmi Ky | Wholesale & retail | 1994 |