| Autokoulu Lilliputti Oy | Education | 2006 |
| Autokoulu Pasila Oy | Education | 1995 |
| Autokoulu Start Oy | Education | 2011 |
| Autokraatti Oy | Real estate | 1987 |
| Autoks Finland Oy | Education | 2010 |
| Autokuume Oy | Wholesale & retail | 1988 |
| Autolasipalvelu Oy Koskela & Savolainen | Construction | 1975 |
| Autoliike Palomäki Oy | Wholesale & retail | 2013 |
| Automaalaamo & huolto Kirjavainen Oy | Other services | 2003 |
| Automaalaamo Haverinen Oy | Other services | 2014 |
| Automaalaamo Rex Oy | Other services | 2021 |
| Automaalaamo Tilulilu Oy | Other services | 2002 |
| Automaatioväylä Oy | Information & communication | 1991 |
| Automaatti-Hoikkala Oy | Administrative & support | 1990 |
| Automagic Solutions Oy | Information & communication | 2020 |
| Automaja Oy | Wholesale & retail | 2016 |
| Automated Smoke Test Oy | Information & communication | 2020 |
| Automatrix Oy | Wholesale & retail | 2000 |
| Automaxi Oy | Wholesale & retail | 2006 |
| Automaxine Oy | Wholesale & retail | 2020 |
| Automediat.com Oy | Information & communication | 1998 |
| Automotive Investment Group Oy | Financial services | 2025 |
| Automous Oy | Information & communication | 2023 |
| Auton Nanomeikkaus Oy | Other services | 2026 |
| Autonasennus ja -huolto Laukkanen Oy | Other services | 1996 |
| Autonhoito Jamine Oy | Other services | 1995 |
| Autonomia Oy | Financial services | 1993 |
| Autonpesu Latva Oy | Other services | 2019 |
| Autopalvelu - 85 Oy | Wholesale & retail | 1986 |
| Autopalvelu Harklin Oy | Other services | 1992 |
| Autopalvelu Kari Toivanen Oy | Transport & logistics | 2004 |
| Autopalvelu Kortelainen Oy | Other services | 2018 |
| Autopalvelu Teuvo J. Saarinen Oy | Other services | 1997 |
| Autopesu Apex Oy | Other services | 2026 |
| Autopesu K&GB Oy | Other services | 2013 |
| Autopesu Kiilto & Loisto Oy | Other services | 2025 |
| Autopilotti Sijoitus Oy | Wholesale & retail | 2015 |
| Autopilotti Suomi Oy | Wholesale & retail | 2015 |
| Autorep Oy | Wholesale & retail | 1991 |
| Autorun Oy | Information & communication | 2008 |
| Autotest Oy | Professional & scientific | 2011 |
| Autotieto Oy | Information & communication | 1936 |
| Autotitan Oy | Other services | 2023 |
| Autotorppa Oy | Wholesale & retail | 2005 |
| Autotrans Ky | Transport & logistics | 1983 |
| Autovista Oy | Information & communication | 1987 |
| Autovuokraus Puro Oy | Administrative & support | 2017 |
| Autoyksikkö Oy | Other services | 2022 |
| Autre Chose Café Oy | Hospitality | 2015 |
| Auttavat kädet kotiin Oy | Health & social care | 2020 |
| Autto Law & Design Oy | Professional & scientific | 2023 |
| Auventur Oy | Professional & scientific | 2025 |
| Auvin Oy | Administrative & support | 2017 |
| Auvinen Yhtiöt Oy | Financial services | 2009 |
| Ava Training & Media Oy | Education | 2018 |
| Avaa Sydämesi Oy | Health & social care | 2023 |
| Avaajat avoin yhtiö | Information & communication | 2024 |
| Avaario Oy | Information & communication | 2026 |
| Avaava Digital Oy | Information & communication | 2017 |
| Avaava Oy | Real estate | 2015 |
| Avail Asianajotoimisto Oy | Professional & scientific | 2021 |
| Availor Oy | Financial services | 2020 |
| Avain Asumisoikeus Holding Oy | Real estate | 2023 |
| Avain Asumisoikeus Oy | Real estate | 2005 |
| Avain Holding Oy | Administrative & support | 1988 |
| Avain Parkki Oy | Transport & logistics | 2021 |
| Avain Rakennuttaja Oy | Construction | 2015 |
| Avain Vuokra Holding Oy | Real estate | 2023 |
| Avain Vuokra Oy | Real estate | 2011 |
| Avain Vuokra-asunnot 2 Oy | Real estate | 2021 |
| Avain Vuokra-asunnot 3 Oy | Real estate | 2022 |
| Avain Vuokra-asunnot 4 Oy | Real estate | 2022 |
| Avain Vuokra-asunnot 5 Oy | Real estate | 2023 |
| Avain Vuokra-asunnot Oy | Real estate | 2016 |
| Avain Vuokra10 Oy | Real estate | 2012 |
| Avain Vuokrakodit Oy | Real estate | 2012 |
| Avain Vuokratalot Oy | Real estate | 2016 |
| Avain Yhtiöt Oy | Real estate | 2010 |
| Avain-Asema Oy | Wholesale & retail | 1986 |
| Avainahjo Oy | Wholesale & retail | 2006 |
| Avainapteekit Oy | Wholesale & retail | 2018 |
| Avainasunto Paavolainen & Kumppanit | Construction | 1979 |
| Avainlippu Oy | Professional & scientific | 1990 |
| Avains Oy | Information & communication | 2016 |
| Avaintec Oy | Information & communication | 1997 |
| Avaintukku Oy | Wholesale & retail | 2019 |
| Avaklus Oy | Professional & scientific | 2010 |
| Aval Ab | Professional & scientific | 1988 |
| Aval Wealth Management Ab | Financial services | 2008 |
| Aval Wealth Management Holding Ab | Financial services | 2022 |
| Avalah Oy | Information & communication | 2026 |
| Avalanche Analytics Oy | Information & communication | 2026 |
| Avalanze Capital Oy | Financial services | 2022 |
| Avallon Oy | Wholesale & retail | 2021 |
| Avalon Sport Oy | Arts & recreation | 2024 |
| Avalue Oy | Real estate | 2019 |
| Avam OY | Wholesale & retail | 2022 |
| Avama Oy | Health & social care | 2021 |
| Avamare Oy | Professional & scientific | 2001 |
| Avamo Oy | Wholesale & retail | 2014 |