| Aligrundets Vattenandelslag | Water & waste | 2000 |
| Amber Branch Ab | Agriculture & fishing | 2020 |
| Amida Hallen Ab Oy | Wholesale & retail | 2006 |
| Amidamer Oy | Wholesale & retail | 2024 |
| Amplify Marketing öppet bolag | Professional & scientific | 2026 |
| Analytical Solutions B Ab | Professional & scientific | 2018 |
| Anchor Ventures Oy Ab | Wholesale & retail | 2022 |
| Anchor Ventures Tpc 1 Kb | Financial services | 2025 |
| Anciterra Oy Ab | Wholesale & retail | 1996 |
| Andelslaget Folkhemmet | Financial services | 1916 |
| Andelslaget Socklot-Nabba vintervatten | Water & waste | 2026 |
| Animae Ab | Hospitality | 2024 |
| Anna daghem Ab | Education | 2015 |
| Antonomia Ab | Professional & scientific | 2008 |
| Ar Ge Marine Ab | Construction | 2026 |
| Aranor Oy | Wholesale & retail | 2005 |
| Arctic Legend Ab | Wholesale & retail | 2015 |
| Arkkitehtitoimisto Jorma Toivonen Oy | Professional & scientific | 1989 |
| Arktis Productions Ab | Arts & recreation | 2018 |
| Arnt Oy | Professional & scientific | 2023 |
| Arrogram Ab Oy | Wholesale & retail | 2017 |
| Asennus Suonperä Oy | Construction | 2023 |
| Asian Garden Restaurant Öppet bolag | Hospitality | 2012 |
| Asianajotoimisto Torato Juridik Oy | Professional & scientific | 2015 |
| Aspen Rakennuspalvelu Oy | Construction | 2021 |
| Assets KP Oy | Professional & scientific | 2010 |
| Astemes Ab | Information & communication | 2021 |
| Aurepirtti Oy | Real estate | 1995 |
| Aurora Motors Ab | Wholesale & retail | 2025 |
| Auto Delight Ab | Wholesale & retail | 2021 |
| Auto Pro Center Ab Oy | Wholesale & retail | 2023 |
| Auto-Center Järn & Strömbäck Ab | Wholesale & retail | 2004 |
| Auto-Trade A Sandström Ab | Wholesale & retail | 2002 |
| Autokorjaamo Hautamäki, avoin yhtiö | Other services | 1994 |
| Automek Lindgren Ab | Other services | 2012 |
| Aventus Development Oy | Financial services | 2025 |
| Aware Games Andelslag | Information & communication | 2014 |
| Azure Capital AB | Wholesale & retail | 1994 |
| B-Fox Ab | Agriculture & fishing | 2011 |
| B2BImport Ab | Wholesale & retail | 2023 |
| BBQ Brothers Oy | Hospitality | 2022 |
| BC Prospect Oy Ab | Arts & recreation | 2024 |
| BD-Invest Ab Oy | Construction | 2017 |
| BIFRAMTEC öppet bolag | Information & communication | 2017 |
| BJERF Ab | Financial services | 2021 |
| BNR-Kiinteistöt Oy Ab | Real estate | 2008 |
| BS-Metall Ab Oy | Manufacturing | 1992 |
| BTB Transformers Ab | Manufacturing | 2005 |
| BW Business öppet bolag | Wholesale & retail | 2005 |
| Bahardent Ab | Health & social care | 2023 |
| Baltic Clean Finland Holding Oy Ab | Other services | 2016 |
| Baltic Yachts Oy Ab Ltd | Manufacturing | 1989 |
| Baran Tekin avoin yhtiö | Hospitality | 2023 |
| Bay of Bothnia Marine Surveys Oy | Transport & logistics | 2018 |
| BeSharp holding Ab | Financial services | 2026 |
| Beamex Oy Ab | Manufacturing | 1975 |
| Beerworld Ab Oy | Wholesale & retail | 2013 |
| Begravningsbyrå E. Johansson Ab | Other services | 1995 |
| Ben's Berry Ab | Wholesale & retail | 2016 |
| Bennys Service Ab | Construction | 2017 |
| Bibi Dental Ab | Health & social care | 2011 |
| Billerud Finland Oy | Manufacturing | 2011 |
| Bilskola Akso Ab | Education | 2022 |
| Biskops Järn och Inredning Ab - Biskops Rauta ja Sisustus Oy | Wholesale & retail | 1979 |
| Bjorkstrom Oy Ab | Information & communication | 2019 |
| Björk Snickeri Ab | Construction | 2023 |
| Björntjänst Ab | Education | 2023 |
| Black Sheep Pub & Terrace Ab | Hospitality | 2014 |
| BlackLightHouse Oy | Information & communication | 2021 |
| Blackbird Holding Oy | Financial services | 2025 |
| BloomiApp Ab | Professional & scientific | 2025 |
| Blue Particle Media Avoin Yhtiö | Information & communication | 2009 |
| Bokföringsbyrå Prima Ab | Professional & scientific | 2021 |
| Bokföringsbyrå Tililaskenta Ab - Tilitoimisto Tililaskenta Oy | Professional & scientific | 1997 |
| Boode Oy | Professional & scientific | 2008 |
| Boost Buddies Ab | Professional & scientific | 2023 |
| Boosti Pietarsaari Oy | Wholesale & retail | 2025 |
| Borgmästars Svets Ab | Manufacturing | 1990 |
| Bostads Ab Södermalm Asunto Oy | Real estate | 1915 |
| Botnia Andelsbank | Financial services | 1939 |
| Botnia Horecapalvelut Oy | Wholesale & retail | 2020 |
| Botnia Rationem Ab Oy | Professional & scientific | 2024 |
| Botnia Villa Oy Ab | Real estate | 2020 |
| Brankeborg Ab | Hospitality | 2019 |
| Bredbacka Consulting Company Ab | Professional & scientific | 2015 |
| Bredbacka Invest Ab Oy | Real estate | 2017 |
| Brewer Sailing Ab | Professional & scientific | 2010 |
| Bri-Bo Ab | Manufacturing | 2018 |
| Bridge Network Oravais Ab | Information & communication | 2016 |
| BrightKem Oy | Wholesale & retail | 2019 |
| Brilliant Cleaning Ab Oy | Administrative & support | 2017 |
| Brisa Ab Oy | Wholesale & retail | 1995 |
| Bro Print Oy | Manufacturing | 2021 |
| Broowood avoin yhtiö | Manufacturing | 2014 |
| Bröderna Granqvists Bilservice | Wholesale & retail | 1977 |
| ByggRak Consulting Ab | Professional & scientific | 2007 |
| Byggnads Ab Nynäs Rakennus Oy | Construction | 1972 |
| Byggtjänst Eklund Ab Oy | Construction | 2017 |
| Byggtjänst Långnabba Ab | Construction | 1988 |
| Byproduct Games Oy | Manufacturing | 2025 |