| Auto-Rasku Oy | Wholesale & retail | 2002 |
| Auto-Strada Oy | Wholesale & retail | 1982 |
| AutoJevi Oy | Other services | 2019 |
| Autofiksaus Vento Oy | Other services | 1989 |
| Autofix Team Oy | Other services | 2019 |
| Autohallin Autokoulu Oy | Education | 2006 |
| Autohuolto Harkka avoin yhtiö | Real estate | 1993 |
| Autohuolto ja -myynti SC Oy | Other services | 2023 |
| Autokorjaamo Auto-Salo Oy | Other services | 1996 |
| Autokorjaamo Enlund oy | Other services | 2023 |
| Autokorjaamo Highwey Oy | Other services | 2022 |
| Autokorjaamo Leskinen & Loponen, avoin yhtiö | Other services | 1990 |
| Autokorjaamo Lipposet | Other services | 1995 |
| Autokoulu Ajaxx Company Oy | Education | 1993 |
| Autokoulu RSA Oy | Education | 2021 |
| Autokoulu Safiiri Oy | Education | 1966 |
| Autoliike Auto-Lempinen Oy | Wholesale & retail | 1985 |
| Autolukkotaiturit Oy | Other services | 2025 |
| Automaailma Group Oy | Wholesale & retail | 2021 |
| Automaalaamo Salmi Oy | Other services | 2019 |
| Automaatiokonsultointi Dietrich Oy | Professional & scientific | 2014 |
| Automation Garage Oy | Manufacturing | 2017 |
| Automobile Holding Oy | Financial services | 2019 |
| Autopeltityö Koivumäki Oy | Other services | 2016 |
| Autoplan Oy | Professional & scientific | 2019 |
| Autosähkö Kaarilahti Oy | Other services | 1990 |
| Autosähkö ja Dieselhuolto Oy Häkkinen | Other services | 1984 |
| Autotalliyhtiö Vainio ja kumppanit | Real estate | 2011 |
| Autotalo Kylmä Oy | Wholesale & retail | 2026 |
| Autotalo MS Oy | Wholesale & retail | 2023 |
| Autotalo Mattinen Oy | Real estate | 2018 |
| Autotalo Sherif Oy | Wholesale & retail | 2019 |
| Auvo-Palvelut Oy | Education | 2017 |
| Avainkeskus skanssi Oy | Manufacturing | 2023 |
| Avainn oy | Arts & recreation | 2023 |
| Avalon Investing Oy | Financial services | 2018 |
| Avanelle Holdings Oy | Financial services | 2025 |
| Avanor Oy | Construction | 2011 |
| Avant Service Oy Ab Ltd | Construction | 2017 |
| Avanti Invest Oy | Financial services | 2011 |
| Avanti Properties 1 Oy | Real estate | 2023 |
| Avanto Exposure Oy | Health & social care | 2017 |
| Avanzarex Anl | Professional & scientific | 2025 |
| Avaon Oy | Professional & scientific | 2019 |
| Avar-Group Oy | Real estate | 2017 |
| Avara Lasitus Oy | Construction | 2026 |
| Avatele Oy | Professional & scientific | 2008 |
| Avato Oy | Financial services | 2014 |
| Avea-asunnot Oy | Real estate | 2024 |
| Avenco Oy | Wholesale & retail | 2019 |
| Avensis Capital Oy | Financial services | 2013 |
| Averno Oy | Professional & scientific | 2012 |
| Avertas Oy | Administrative & support | 2003 |
| Avertas Robot Service Oy | Manufacturing | 2026 |
| Avertas Robotics Oy | Manufacturing | 2007 |
| Aveso Oy | Information & communication | 2014 |
| Avetrix Oy | Financial services | 1994 |
| Aviato Holdings Oy | Financial services | 2021 |
| Avid Oy | Wholesale & retail | 2025 |
| Avinto Holding Oy | Real estate | 2017 |
| Avium Oy | Health & social care | 1992 |
| Avoin Maailma Holding Oy | Information & communication | 2018 |
| Avoin Maailma Oy | Information & communication | 2020 |
| Avoin Yhtiö Hirvoila | Wholesale & retail | 2012 |
| Avoin Yhtiö Maanpään Aurinkorannat | Real estate | 1989 |
| Avoin Yhtiö VIVID DANCERS | Arts & recreation | 2013 |
| Avoin yhtiö Dark Noise Productions | Arts & recreation | 2008 |
| Avoin yhtiö Hakapellonkatu 2, Turku | Real estate | 2024 |
| Avoin yhtiö Hautaustoimisto-Begravningsbyrå Saarinen | Other services | 1981 |
| Avoin yhtiö Havana Pub | Hospitality | 1990 |
| Avoin yhtiö KS Kustoms | Construction | 2009 |
| Avoin yhtiö Kevytpyörä M ja M Lahti | Wholesale & retail | 1982 |
| Avoin yhtiö Maanpään Kesämaa | Real estate | 2014 |
| Avoin yhtiö Maanpään Lokkiranta | Real estate | 1998 |
| Avoin yhtiö Puosi & Stenberg | Real estate | 2008 |
| Avoin yhtiö Susu-Sport | Wholesale & retail | 2014 |
| Avoin yhtiö T&R Kotiranta | Wholesale & retail | 2010 |
| Avoin yhtiö Turun Tuulilasimyynti | Manufacturing | 1997 |
| Avoin yhtiö Winter's Stable | Arts & recreation | 2015 |
| Avore Media Oy | Professional & scientific | 2024 |
| Avorius Oy | Real estate | 2022 |
| Avramidis-Turkis Oy | Wholesale & retail | 1975 |
| Avril 14 Oy | Professional & scientific | 2023 |
| Avsec Communications Oy | Wholesale & retail | 1997 |
| Avux-Vuokraus Avoin yhtiö | Real estate | 2001 |
| Axfield Oy | Professional & scientific | 2022 |
| Axioms Oy | Professional & scientific | 2015 |
| Axion Aerial Oy | Professional & scientific | 2025 |
| Axis Oy | Health & social care | 2008 |
| Axvio Innovaattorit Oy | Wholesale & retail | 2019 |
| Aylin Oy | Transport & logistics | 2025 |
| Azanta Oy | Wholesale & retail | 2007 |
| Azara Oy | Professional & scientific | 2024 |
| Azmar Oy | Other services | 2015 |
| Azzoti Oy | Professional & scientific | 2007 |
| B Kiinteistöt Oy | Real estate | 2014 |
| B Publishing Oy | Information & communication | 2004 |
| B&B Building Oy | Construction | 2020 |
| B&C Boat & Car OY | Other services | 1991 |
| B&L Deli Oy | Hospitality | 2024 |