| As-Tieto Oy | Professional & scientific | 2010 |
| Asar Oy | Professional & scientific | 2022 |
| Asbo Oy | Construction | 2025 |
| Ascender Oy | Financial services | 2013 |
| Ascenso Oy | Professional & scientific | 2018 |
| Ascentia Ltd Oy | Professional & scientific | 1994 |
| Ascora Oy | Manufacturing | 2014 |
| Aseman Lukko Oy | Wholesale & retail | 2010 |
| Asematunnelin Optiikka Oy | Wholesale & retail | 1990 |
| Asenion Estate Oy | Real estate | 2010 |
| Asennus - Pirttilahti Oy | Construction | 2007 |
| Asennus Aran Oy | Construction | 2003 |
| Asennus-Redi Oy | Construction | 1993 |
| Asennusliike Lahtinen Oy | Construction | 2012 |
| Asennuspalvelu Control Oy | Construction | 2011 |
| Asennuspalvelu Kosunen Oy | Wholesale & retail | 2018 |
| Asennuspalvelu Lönnström Oy | Manufacturing | 2018 |
| Asensiot Oy | Information & communication | 2017 |
| Asetor Oy | Financial services | 2022 |
| Asfaltti Taskinen Oy | Construction | 1996 |
| Asia Exchange Oy | Other services | 2007 |
| Asia Law Partners Ky | Professional & scientific | 1993 |
| Asiakashankinta LT Oy | Professional & scientific | 2025 |
| Asiakkuuskumppanit Oy | Professional & scientific | 2025 |
| Asianajotoimisto ACTAS Oy | Professional & scientific | 1997 |
| Asianajotoimisto Alfa Oy | Professional & scientific | 2016 |
| Asianajotoimisto Annala & Teivaala Oy | Professional & scientific | 2019 |
| Asianajotoimisto Askel Oy | Professional & scientific | 2019 |
| Asianajotoimisto Facta Oy | Professional & scientific | 1993 |
| Asianajotoimisto Gummerus Oy | Professional & scientific | 1975 |
| Asianajotoimisto Hakola Oy | Professional & scientific | 2013 |
| Asianajotoimisto Heikki Penttilä Oy | Professional & scientific | 2020 |
| Asianajotoimisto Jari Hytti Oy | Professional & scientific | 2023 |
| Asianajotoimisto Jyrki Mantere Oy | Professional & scientific | 2011 |
| Asianajotoimisto Kari Miettinen & Co Oy | Professional & scientific | 2002 |
| Asianajotoimisto Kari Miettinen Ky | Professional & scientific | 1997 |
| Asianajotoimisto Karimaa & Vähätalo Oy | Professional & scientific | 1982 |
| Asianajotoimisto Kilpi, Luukkonen & Toikka | Professional & scientific | 2005 |
| Asianajotoimisto Kuha & Ristimäki Ky | Professional & scientific | 2003 |
| Asianajotoimisto Kunvik & Lehesvuori Oy | Professional & scientific | 2012 |
| Asianajotoimisto Liisa Tarvainen Ky | Professional & scientific | 1987 |
| Asianajotoimisto Luckylaki Oy | Professional & scientific | 2019 |
| Asianajotoimisto Merkurius Oy | Professional & scientific | 2017 |
| Asianajotoimisto Mika Ala-Uotila Oy | Professional & scientific | 1990 |
| Asianajotoimisto Mäkelä & Penttilä Oy | Professional & scientific | 2017 |
| Asianajotoimisto Nieminen & Simola Oy | Professional & scientific | 2013 |
| Asianajotoimisto Outi Korppoo Oy | Professional & scientific | 2015 |
| Asianajotoimisto Pentti Lintulaakso Oy | Professional & scientific | 2008 |
| Asianajotoimisto Pertti Holopainen Oy | Professional & scientific | 2005 |
| Asianajotoimisto Pilviö & Lukkari Oy | Professional & scientific | 2026 |
| Asianajotoimisto Riitta Sommarberg Oy | Professional & scientific | 2015 |
| Asianajotoimisto Roihu Oy | Professional & scientific | 2010 |
| Asianajotoimisto Sillanpää Oy | Professional & scientific | 2018 |
| Asianajotoimisto Suojanen & Alanen Oy | Professional & scientific | 2000 |
| Asianajotoimisto Tammer-Juristit Oy | Professional & scientific | 1996 |
| Asianajotoimisto Tampereen Lakitalo Oy | Professional & scientific | 2018 |
| Asianajotoimisto Tarmo Lahtinen Ky | Professional & scientific | 1995 |
| Asianajotoimisto Tatu Pylvänäinen Oy | Professional & scientific | 2024 |
| Asianajotoimisto Tempo Oy | Professional & scientific | 2010 |
| Asianajotoimisto Tuutti Oy | Professional & scientific | 1990 |
| Asianajotoimisto Veneskoski Oy | Professional & scientific | 2008 |
| Asiantuntijaosuuskunta Edu-O-Matic | Education | 2015 |
| Asim Recycling Oy | Manufacturing | 2020 |
| Asioidenhoitopalvelu Matinniemi Oy | Professional & scientific | 2020 |
| Askel Healthcare Oy | Professional & scientific | 2017 |
| Askel Management Oy | Professional & scientific | 2021 |
| Askelia Oy | Health & social care | 2019 |
| Askosaari Oy | Wholesale & retail | 1992 |
| Asma Partners Oy | Wholesale & retail | 2007 |
| Asma Samir Oy | Hospitality | 2020 |
| Asnor Oy | Construction | 2007 |
| Aspark Oy | Information & communication | 2024 |
| Aspeni Oy | Construction | 2017 |
| Aspenwood Advisory Oy | Professional & scientific | 2013 |
| Assari Lounge Collective Oy | Professional & scientific | 2026 |
| Asser Investments Oy | Financial services | 2022 |
| Asset Office Oy | Professional & scientific | 1994 |
| Assetia Oy | Financial services | 2015 |
| Assistas Oy | Construction | 2024 |
| Assurance Advisory Oy | Professional & scientific | 2019 |
| Astekto Oy | Manufacturing | 1999 |
| Astemix Oy | Arts & recreation | 2021 |
| Asten Solutions Oy | Information & communication | 2026 |
| Astrofy Oy | Information & communication | 2010 |
| Astrologiapalvelut Kuussa ja Maassa Oy | Other services | 2011 |
| Asulux Oy | Real estate | 2017 |
| Asumisoikeus Oy Raision Jarrilantie 2 | Real estate | 2023 |
| Asumisosuuskunta Aunen ja Erkin Koti | Real estate | 2020 |
| Asumisosuuskuntien Kehitys Askeosku Oy | Real estate | 2020 |
| AsunTuomaiset Oy | Professional & scientific | 2023 |
| Asustamo Oy | Wholesale & retail | 2020 |
| Asuva Oy | Construction | 1990 |
| At Night Entertainment Oy | Professional & scientific | 2014 |
| Ata Gears Oy | Manufacturing | 1937 |
| Atalvest Oy | Real estate | 1997 |
| Atalysti Oy | Information & communication | 2022 |
| Atapley Europe Oy | Professional & scientific | 2024 |
| Atek Oy | Manufacturing | 2021 |
| Ateljeekatu osk | Arts & recreation | 2006 |
| Ateljeetalo Oy | Real estate | 1961 |