| Annas Vatten Ab | Water & waste | 2016 |
| Anncas Health&Herbs Ab | Wholesale & retail | 2020 |
| Antei Monoliitti Oy | Construction | 2021 |
| Antihero Studios Oy | Information & communication | 2024 |
| Antikwest Finland Ab | Wholesale & retail | 1990 |
| Aortae Holding Oy | Financial services | 2006 |
| Aota Oy | Hospitality | 2017 |
| ApexStaff OY | Administrative & support | 2023 |
| Apollo Education Oy | Education | 2018 |
| Apu Teille Oy | Transport & logistics | 2020 |
| Apukaveri Oy | Administrative & support | 2020 |
| Apuresurssi Oy | Construction | 2009 |
| Aquatic Energy Systems Oy | Professional & scientific | 2020 |
| Arabesque Oy | Hospitality | 2018 |
| Aram Group Oy | Hospitality | 2023 |
| Aramhat oy | Other services | 2023 |
| Arcelevn Oy | Wholesale & retail | 2020 |
| Arcosin Oy | Professional & scientific | 1991 |
| Arctic Solar Oy | Manufacturing | 2020 |
| Argonimation Oy | Professional & scientific | 2013 |
| Arif Frank Oy | Other services | 2020 |
| Arkkitehtitoimisto Salerno Arkkitehdit Oy | Professional & scientific | 2005 |
| Armazur Oy | Other services | 2020 |
| Arnis-Konsultointi Oy | Information & communication | 1989 |
| Aro autopalvelut Oy | Wholesale & retail | 2020 |
| Aroos Damascus Resturant Oy | Hospitality | 2021 |
| Arrow Holdings Oy | Professional & scientific | 2023 |
| ArtoPalvelu Oy | Construction | 2019 |
| Arunika Amerta Oy | Professional & scientific | 2022 |
| Arvo Mobile Oy | Financial services | 2016 |
| Arza-Trading Co Oy | Wholesale & retail | 1991 |
| Aseliike A. Kannisto Ky | Wholesale & retail | 1988 |
| Asheer Trade Oy | Wholesale & retail | 2019 |
| Asiakassuhdetoimisto Circus Oy | Professional & scientific | 2001 |
| Asiakastietolomake Suomi Oy | Information & communication | 2019 |
| Asianajotoimisto Haapaniemi Oy | Professional & scientific | 2017 |
| Asil Oy | Hospitality | 2024 |
| Asioimisto Oy HKM | Professional & scientific | 2000 |
| Asman Oy | Hospitality | 2019 |
| Asmar Events Oy | Other services | 2022 |
| Aspoo Oy | Wholesale & retail | 2013 |
| Assistee Oy | Other services | 2023 |
| Astronix Oy | Manufacturing | 1988 |
| Atelier Elegantti Oy | Professional & scientific | 2021 |
| Atlasbalans OY | Professional & scientific | 2018 |
| Atmotek Oy | Construction | 2020 |
| Attitude dancewear Oy | Wholesale & retail | 2016 |
| Attraversiamo Oy | Hospitality | 2009 |
| AuRak Oy | Construction | 2020 |
| Audiokirppis Oy | Wholesale & retail | 2022 |
| Audioprima Oy | Construction | 1994 |
| Aura LKV Oy | Real estate | 2018 |
| Auringosta Energiaa Oy | Construction | 2023 |
| Aurium Technology Oy | Construction | 2019 |
| Aurora Metals Oy | Wholesale & retail | 2019 |
| Aurora Miracle Oy | Wholesale & retail | 2017 |
| Aurora Sulka Oy | Arts & recreation | 2022 |
| Aurorahelmi Oy | Wholesale & retail | 2009 |
| Aurum Imports & Exports Oy | Wholesale & retail | 2023 |
| Auto & Vanne Oy | Wholesale & retail | 2021 |
| Auto Dolly Oy | Wholesale & retail | 2015 |
| Auto Fusion Oy | Wholesale & retail | 2024 |
| Auto Polar Oy | Other services | 2022 |
| Auto- ja Konesähkö Bengs Oy | Other services | 1983 |
| Auto-Cleanfix OY | Other services | 2021 |
| Auto-Liipasin Oy | Real estate | 1984 |
| Auto2one oy | Other services | 2020 |
| AutoAN Oy | Other services | 2022 |
| AutoKylä Oy | Wholesale & retail | 2021 |
| AutoRaj Oy | Other services | 2021 |
| AutoTune Finland Oy | Wholesale & retail | 2011 |
| Autohenri Oy | Other services | 2022 |
| Autohuolto Juntunen OY | Other services | 2024 |
| Autohuolto Sarre Oy | Other services | 2021 |
| Autohuolto Suvanto Oy | Wholesale & retail | 2011 |
| Autokorjaamo Drive-In Oy | Other services | 2018 |
| Autokoulu Eufrat oy | Education | 2018 |
| Autokoulu Koutsi Oy | Education | 2020 |
| Autolab Service Oy | Other services | 2024 |
| Autolania Oy | Other services | 2018 |
| Autoliike Emet Oy | Wholesale & retail | 2017 |
| Autolääkäri Oy | Other services | 2024 |
| Automarket Finland Oy | Wholesale & retail | 2003 |
| Automeko Korjaamo Oy | Construction | 2013 |
| Automyynti Max Oy | Wholesale & retail | 2021 |
| Autonjäähdyttäjäliike Valkonen Oy | Transport & logistics | 1952 |
| Autoparts United Finland Oy | Financial services | 2022 |
| Autoparts United Nordic Oy | Professional & scientific | 2022 |
| Autopesu Kamppi Oy | Other services | 2019 |
| Autopesula Mix Oy | Other services | 2021 |
| Autosi takuu Oy | Financial services | 2024 |
| Autosynkro Oy | Other services | 2014 |
| Autotalo Lindström Oy | Wholesale & retail | 2022 |
| Autotalo Maat Oy | Wholesale & retail | 2020 |
| Autotarvike Leino Oy | Wholesale & retail | 2025 |
| Autowholesale Automotive Finland Oy | Wholesale & retail | 2015 |
| Availab Palvelut Oy | Wholesale & retail | 2020 |
| Avain China Holding Oy | Professional & scientific | 2013 |
| Avainhoiva Oy | Health & social care | 2021 |
| Avalog Oy | Construction | 2015 |