| Arvohoiva Oy | Health & social care | 2020 |
| Arvoholding Oy | Real estate | 2019 |
| Arvoista Oy | Professional & scientific | 2022 |
| Arvokartasto Oy | Professional & scientific | 2025 |
| Arvokas Asunnot Oy | Financial services | 2017 |
| Arvokas Investment Oy | Professional & scientific | 2013 |
| Arvokas Mieli Oy | Health & social care | 2018 |
| Arvokatalogi Oy | Wholesale & retail | 2025 |
| Arvokoneisto Oy | Wholesale & retail | 2025 |
| Arvokonseptit Oy | Administrative & support | 2011 |
| Arvokoru Oy | Wholesale & retail | 2024 |
| Arvokukka Oy | Wholesale & retail | 2011 |
| Arvolukko Oy | Construction | 2001 |
| Arvom2 LKV Oy | Education | 2002 |
| Arvometalli Oy Suomi | Wholesale & retail | 2011 |
| Arvomis Oy | Information & communication | 2025 |
| Arvon perintö Oy | Professional & scientific | 2020 |
| Arvonen Investments Oy | Financial services | 2016 |
| Arvoni Oy | Health & social care | 2022 |
| Arvonia Oy | Arts & recreation | 2019 |
| Arvonosturi Oy | Professional & scientific | 2020 |
| Arvopakki Oy | Professional & scientific | 2025 |
| Arvosa Oy | Professional & scientific | 2025 |
| Arvotakojat Oy | Education | 2008 |
| Arvotalo Kiinteistönvälitys LKV Oy | Real estate | 2013 |
| Arvotar talous- ja liiketoimintakonsultointi Oy | Professional & scientific | 2025 |
| Arvotase Oy | Real estate | 2019 |
| Arvotekijät Suomi Oy | Financial services | 2011 |
| Arvotitaanit Oy | Professional & scientific | 1989 |
| Arvotuotanto Ky | Information & communication | 2012 |
| Arvotähti Oy | Wholesale & retail | 2026 |
| Arvoverkko Oy | Professional & scientific | 2002 |
| Aryilin katukeittiö Oy | Hospitality | 2025 |
| Aryos parturi kampaamo Oy | Other services | 2023 |
| Arysume digital Oy | Professional & scientific | 2025 |
| Arzun katukeittiö Oy | Hospitality | 2025 |
| As Oy Tuusulan OlympiaKasarmi | Real estate | 2019 |
| As Oy:n Tilipalvelu AT Oy | Professional & scientific | 1995 |
| As Panis Oy | Real estate | 1998 |
| Asad Friigym Oy | Transport & logistics | 2020 |
| Asadin Oy | Professional & scientific | 2001 |
| Asagiri Oy | Financial services | 2025 |
| Asahi Partners Oy | Professional & scientific | 2012 |
| Asana Helsinki Oy | Education | 2017 |
| Asap autohuolto Oy | Other services | 2024 |
| Asare Partners Oy | Professional & scientific | 2011 |
| Asbestikartoitus Etelä-Suomi Oy | Construction | 2024 |
| Asbrak Oy | Water & waste | 1987 |
| Ascendant Consulting Group Oy | Education | 2024 |
| Ascension Oy | Professional & scientific | 2010 |
| Ascently Oy | Professional & scientific | 2023 |
| Aschan Consulting Ab | Information & communication | 2018 |
| Asclepius Oy | Health & social care | 2009 |
| Asclepius Ventures Oy | Financial services | 2024 |
| Asd Consulting Oy | Professional & scientific | 2024 |
| Asean Bistro Oy | Hospitality | 2024 |
| Aseanic Trading Oy | Wholesale & retail | 1994 |
| Asehuolto MW Oy | Wholesale & retail | 1994 |
| Asema Consulting Oy | Information & communication | 2000 |
| Aseman Kello Airport Oy | Wholesale & retail | 1986 |
| Aseman Kello Oy | Real estate | 1955 |
| Asemansuutari Oy | Other services | 1969 |
| Asematunnelin Kuvapiste Oy | Wholesale & retail | 1985 |
| Asemota´s Palvelu & Taksi Helsinki avoin yhtiö | Transport & logistics | 2025 |
| Asenne Oy | Real estate | 1995 |
| Asennemedia Oy | Professional & scientific | 2015 |
| Asennemuija Oy | Arts & recreation | 2020 |
| Asennesiivous Oy | Administrative & support | 1991 |
| Asennus-, Huolto- & Korjaustyöt Heikkonen OY | Real estate | 2022 |
| Asennus-Iskanius Oy | Construction | 2022 |
| Asennusliike A. Nieminen Oy | Construction | 2002 |
| Asennuspalvelu Mali Oy | Construction | 2021 |
| Ases Oy | Hospitality | 2024 |
| Asesis Oy | Financial services | 2026 |
| Asetekno Oy | Manufacturing | 1974 |
| Asfaltti Kuntoon Oy | Construction | 2026 |
| Asfalttiasiantuntijat Oy | Professional & scientific | 2026 |
| Asfalttikukka Oy - Asfaltblomman Ab | Administrative & support | 1994 |
| Asfalttiliike E. Lidman Oy | Construction | 1958 |
| Asfalttimaalaus es Oy | Construction | 2009 |
| Asfalttipojat Oy | Construction | 2003 |
| Ashabobo Biosciences Oy | Professional & scientific | 2024 |
| Ashfield Nordic Oy | Professional & scientific | 2001 |
| Ashford Environmental Services Oy | Construction | 2020 |
| Asiakas Group Oy | Professional & scientific | 2023 |
| Asiakas360 Oy | Information & communication | 2021 |
| Asiakaskokemus Savonen Oy | Professional & scientific | 2024 |
| Asiakastutkimusakatemia Oy | Professional & scientific | 2023 |
| Asiakkuustalo Fundament Oy | Professional & scientific | 2018 |
| Asiamiespalvelu A Mäkelä Oy | Professional & scientific | 2016 |
| Asian Food and Beverage Oy | Hospitality | 2021 |
| Asian Trade Lotus Oy | Wholesale & retail | 2021 |
| Asianajotoimisto AP Law Office Oy | Professional & scientific | 2012 |
| Asianajotoimisto Aasa-Law Oy | Professional & scientific | 1997 |
| Asianajotoimisto Advocare-Patrick Lindgren Oy Ab Advokatbyrå | Professional & scientific | 1995 |
| Asianajotoimisto Advoline Oy | Professional & scientific | 2007 |
| Asianajotoimisto Aika Oy | Professional & scientific | 2021 |
| Asianajotoimisto Airaksinen Oy | Professional & scientific | 2016 |
| Asianajotoimisto Alasaari & SPJ Kommandiittiyhtiö | Professional & scientific | 2010 |
| Asianajotoimisto Aleksandra Oy | Professional & scientific | 2016 |