| Améi Nordic Beauty Care Oy | Wholesale & retail | 2025 |
| Ana Bekteshi Ky | Other services | 2019 |
| Anair Holding Oy | Financial services | 2019 |
| Ancro Oy | Education | 2017 |
| Andelslaget Trojkan | Agriculture & fishing | 2014 |
| Andelslaget Österbottens Kött | Wholesale & retail | 1944 |
| Anders Landgärds Ab | Financial services | 1986 |
| Anderssén & Kurki Ab | Wholesale & retail | 2014 |
| Anmaiark Ky | Professional & scientific | 2011 |
| Anna Höglund Productions Ab Oy | Education | 2018 |
| Annala & Kurtén Kiinteistönvälitys Oy LKV - Fastighetsförmedling Ab AFM | Real estate | 2007 |
| Annie Herkut Oy | Wholesale & retail | 2026 |
| Antennihuolto Ikonen Ky | Other services | 1985 |
| Antiikin ja vanhan tavaran liike Prenikka Ky | Wholesale & retail | 2010 |
| Aohe Oy | Hospitality | 2023 |
| Apache Inn Avoin yhtiö | Hospitality | 1998 |
| ApoMed Oy | Wholesale & retail | 2005 |
| Apollo Capital Oy Ab | Professional & scientific | 2022 |
| Apollo Invest Oy | Real estate | 2022 |
| Apollo Photo Oy | Information & communication | 2020 |
| Aquatic Energy Solutions Oy | Professional & scientific | 2023 |
| Aquila Clean Energy Finland Oy | Financial services | 2021 |
| Arcareon oy | Wholesale & retail | 2025 |
| Archoil Finland Oy | Wholesale & retail | 2015 |
| Arcpro Ab | Real estate | 2004 |
| Arcteq Relays Oy | Professional & scientific | 2010 |
| Arcto Ab | Professional & scientific | 2003 |
| Areha Group Oy Ab | Hospitality | 2026 |
| Arish Edge Oy | Hospitality | 2026 |
| Arkipelaga Ltd Ab | Professional & scientific | 2012 |
| Arkitektbyrå Gunilla Lång-Kivilinna Ab | Professional & scientific | 2002 |
| Arkkitehdit Rintamäki Viljanen+J Oy | Professional & scientific | 1989 |
| Arkkitehtitoimisto ALW-Ark Oy | Professional & scientific | 1982 |
| Arkkitehtitoimisto Bäckman & Dunseath Oy | Professional & scientific | 2019 |
| Aroc Kiinteistöt Oy | Real estate | 2020 |
| Arosusi Oy | Information & communication | 2024 |
| Artistum Oy | Arts & recreation | 1989 |
| Arvomaatti Oy | Information & communication | 2016 |
| Asante Oy | Health & social care | 2016 |
| Asianajotoimisto Aawa Oy | Professional & scientific | 2017 |
| Asianajotoimisto Aki Aapio Oy | Professional & scientific | 2024 |
| Asianajotoimisto Keravuori & Lind Kommandiittiyhtiö | Professional & scientific | 1975 |
| Asianajotoimisto Keravuori & Palm Oy | Professional & scientific | 1985 |
| Asianajotoimisto Träskbäck & Co Oy | Professional & scientific | 2024 |
| Aspen Garage Oy | Wholesale & retail | 2022 |
| Aspen Properties Oy | Financial services | 2018 |
| Aspia Finland Oy | Professional & scientific | 2018 |
| Asplund services Ab | Administrative & support | 2021 |
| Asuintalo-osuuskunta Apu | Real estate | 1912 |
| Ateljé 3 Ky | Wholesale & retail | 2015 |
| Ateljé Sari Haapaniemi Avoin yhtiö | Wholesale & retail | 2003 |
| Audiotec Kakkori Ky | Professional & scientific | 1993 |
| Auga Solutions Oy Ab | Information & communication | 2010 |
| Aula Partners Oy | Financial services | 2024 |
| Aura Leaf Oy | Hospitality | 2025 |
| Aurelia Kiinteistöt Oy | Real estate | 2025 |
| Aurora Advisors Oy | Professional & scientific | 2025 |
| Aurora Look Oy | Construction | 2020 |
| AuroraDelta Oy | Professional & scientific | 2025 |
| Aurum Coaching Oy | Education | 2023 |
| Aurum Homes Oy | Real estate | 2025 |
| Auto-Finder Oy | Wholesale & retail | 2003 |
| Auto-Hatanmaa Oy Ab | Wholesale & retail | 1995 |
| AutoRocker öppet bolag | Manufacturing | 2016 |
| Autohuolto Velj. Paulaharju | Wholesale & retail | 1963 |
| Autokierrätys Pohjanmaa Oy | Water & waste | 2022 |
| Autokorjaamo S. Korpi Oy | Other services | 1978 |
| Autokorjaamo Sahala Oy | Other services | 2017 |
| Autokorjaamo Vierikko Ky | Other services | 1985 |
| Autokoulu Bilskola Traffic Studio Oy Ab | Education | 2015 |
| Autokoulu T. Roine Oy | Education | 1976 |
| Autoliike Lähdemäki Oy | Wholesale & retail | 1974 |
| Automation T&N Ab | Professional & scientific | 2007 |
| Autotalo L Luhtala Oy | Wholesale & retail | 1980 |
| Autovaruste M. Koskimäki Ky | Wholesale & retail | 1978 |
| Avaa Solutions Oy | Information & communication | 2020 |
| Avainet Oy | Professional & scientific | 2017 |
| Avalon Nordic Oy | Construction | 2013 |
| Avendia Oy | Health & social care | 2025 |
| Avenea Oy | Health & social care | 2022 |
| Aveny Café Vasa Ab Oy | Hospitality | 2026 |
| Avoin yhtiö Kimmo & Tuija Laukkanen | Wholesale & retail | 2000 |
| Avoin yhtiö Royal Burger | Hospitality | 1983 |
| Avoin yhtiö Teuvan Päähine | Manufacturing | 1981 |
| Avoin yhtiö Waasa Wood | Manufacturing | 2000 |
| Avonner Oy | Professional & scientific | 2018 |
| Avustajapalvelut Pihla Oy | Health & social care | 2025 |
| Axpo Renewable Finland Oy | Energy | 2022 |
| B2 Impact Oy | Administrative & support | 1991 |
| BBI Group Oy | Professional & scientific | 2003 |
| BD Rent Ab | Administrative & support | 2022 |
| BEMI Smart Home Oy | Information & communication | 2017 |
| BMCon Oy | Professional & scientific | 2024 |
| BMF Capital Oy | Professional & scientific | 2022 |
| BQV Group Oy | Wholesale & retail | 2026 |
| BRYGGEt Oy | Professional & scientific | 2019 |
| BS Electrical Oy | Construction | 2022 |
| Backfield Consulting Oy | Professional & scientific | 2016 |
| Badagi Oy | Hospitality | 2025 |
| Bafa Fit Oy | Arts & recreation | 2018 |