| Arvoka Ky | Construction | 2021 |
| Arvopaperisijoittajat Systems Oy | Real estate | 1992 |
| Arvopolku Osuuskunta | Other services | 2026 |
| Arwi Oy | Information & communication | 2023 |
| Ascorex Oy | Real estate | 1988 |
| Asennus 007 OY | Construction | 2010 |
| Asennus Tanhuala Ky | Construction | 2018 |
| Asennus- ja Huoltopalvelu J.Korri Ky | Manufacturing | 2017 |
| Asennus- ja Suunnittelupalvelu Vatula Oy | Construction | 2025 |
| Asianajotoimisto Aarnilex Oy | Professional & scientific | 2025 |
| Asianajotoimisto Antti Paasonen Oy | Professional & scientific | 2017 |
| Asianajotoimisto Artimo & Co | Professional & scientific | 2005 |
| Asianajotoimisto Fenno Oy | Professional & scientific | 2013 |
| Asianajotoimisto Heikkilä & Kuikka Oy | Professional & scientific | 2019 |
| Asianajotoimisto Henry Saleva Oy | Professional & scientific | 1991 |
| Asianajotoimisto Hytönen Oy | Professional & scientific | 2019 |
| Asianajotoimisto Janne Lundbom Oy | Professional & scientific | 2019 |
| Asianajotoimisto Jantunen, Kaartinen & Siltala Oy | Professional & scientific | 2021 |
| Asianajotoimisto Jäälaakso Oy | Professional & scientific | 2023 |
| Asianajotoimisto Kuukka & Tiainen Oy | Professional & scientific | 1983 |
| Asianajotoimisto Kärkkäinen & Niskanen Oy | Professional & scientific | 1994 |
| Asianajotoimisto Olli Santanen Ky | Professional & scientific | 2014 |
| Asianajotoimisto Pakarinen Oy | Professional & scientific | 2026 |
| Asianajotoimisto S.Tiainen Oy | Professional & scientific | 2016 |
| Asianajotoimisto Tero Matsinen Ky | Professional & scientific | 2008 |
| Asianajotoimisto Toiviainen Oy | Professional & scientific | 2022 |
| Asianajotoimisto Tuomi, Lakka & Metsätähti Oy | Professional & scientific | 2019 |
| Asianajotoimisto Tuomo Tapper Ky | Professional & scientific | 1997 |
| Asianajotoimisto Väinämöisen Oy | Professional & scientific | 2017 |
| Asiantuntijapalvelut Pinnalle Oy | Health & social care | 2022 |
| Asimer Oy | Wholesale & retail | 1995 |
| Asivo Oy | Construction | 2017 |
| Askai Solutions Oy | Information & communication | 2019 |
| Askel isännöinti Oy | Real estate | 2026 |
| Askelvirta Oy | Administrative & support | 2008 |
| Asoft Oy | Information & communication | 2019 |
| Aspectus Oy | Professional & scientific | 2010 |
| Assas Oy | Professional & scientific | 2015 |
| Astracell Oy | Financial services | 2025 |
| At Aurinkopaneelit Oy | Construction | 2019 |
| Atelier Hexaco Oy | Wholesale & retail | 2025 |
| Aterna Group Oy | Information & communication | 2025 |
| Athletica Oy | Arts & recreation | 2019 |
| Atlantis Consulting Oy | Information & communication | 1996 |
| Atlas Rakennus Oy | Construction | 2025 |
| Atlasevo Oy | Information & communication | 2026 |
| Atmentor Oy | Professional & scientific | 1989 |
| Atmestar Ky | | 1979 |
| Audiotron Oy | Arts & recreation | 2020 |
| Audission Oy | Information & communication | 2026 |
| Auera Flow Oy | Health & social care | 2025 |
| Aukio Oy | Professional & scientific | 2020 |
| Aulau Oy | Financial services | 2018 |
| Aune Group Oy | Real estate | 2023 |
| Aurelia Health Oy | Health & social care | 2024 |
| Aurinko Group Oy | Construction | 2025 |
| Aurinkohalssi Rakennus Oy | Construction | 2008 |
| Aurinkoveljekset Oy | Administrative & support | 2007 |
| Auron Energy Nordic Oy | Construction | 2024 |
| Aurora Finance Oy | Professional & scientific | 2025 |
| Aurora Prime Oy | Professional & scientific | 2008 |
| Autioniemi PJA oy | Arts & recreation | 2020 |
| Auto-Mäenpää Oy | Other services | 2026 |
| AutoKaarna Oy | Wholesale & retail | 2018 |
| Autohuolto S ja L Alatalo | Wholesale & retail | 1990 |
| Autohuolto Seppä Oy | Other services | 2023 |
| Autohuolto Tero Pirkkanen Oy | Other services | 2016 |
| Autohuolto Tihmola Oy | Other services | 2020 |
| Autokorjaamo Tähtihuolto Oy | Other services | 2012 |
| Autokoulu Juha Laine Oy | Education | 1987 |
| Autokoulu Koljander Oy | Education | 1965 |
| Autokoulu Menox Oy | Education | 1976 |
| Autoliidi Oy | Other services | 2020 |
| Autoliikkeelle Oy | Wholesale & retail | 2022 |
| Automyynti A&H Oy | Wholesale & retail | 2013 |
| Autopesula Janhonen Oy | Other services | 2010 |
| Autopesula Lielahti Oy | Other services | 2020 |
| Autopesula ja Fiksaamo Oikari Oy | Other services | 1993 |
| Autotalo Lahtinen Oy | Wholesale & retail | 2018 |
| Autovuokraamo Matka-Rent Oy | Administrative & support | 1989 |
| Ava & Eva Oy | Real estate | 2025 |
| Avaintalot Oy | Real estate | 2004 |
| Avartuu Oy | Professional & scientific | 2016 |
| Avaruuspalmu Oy | Manufacturing | 2020 |
| Avenue Bar & Diner Oy | Hospitality | 2021 |
| Aveon Advisors Oy | Financial services | 2018 |
| Aveon Real Estate Oy | Real estate | 2020 |
| Averell ky | Real estate | 1993 |
| Avers Oy | Real estate | 1983 |
| Avesina Oy | Wholesale & retail | 2004 |
| Avesome Oy | Information & communication | 2024 |
| Avinor Oy | Information & communication | 1996 |
| Avoin yhtiö Jyväskylän asemagrilli | Hospitality | 1981 |
| Avoin yhtiö Konsulttineliö | Professional & scientific | 1991 |
| Avoin yhtiö Laukaan Ku-Ha | Agriculture & fishing | 1987 |
| Avoin yhtiö Maja 3 A | Professional & scientific | 1999 |
| Avonova Solutions Oy | Professional & scientific | 2023 |
| Azad21 Oy | Wholesale & retail | 2023 |
| Azrasa Holding Oy | Financial services | 2025 |
| Baaz Group OY | Hospitality | 2025 |