| 1959 Consulting Limited Nuf | Real estate | 2007 |
| 361 Ventures AS | Information & communication | 2017 |
| 4MAUR AS | Information & communication | 2005 |
| 4XM Group AS | | 2024 |
| A Costa Saks AS | Other services | 2001 |
| Aadde Invest AS | | 2026 |
| Aai Bilruta Eiendom AS | Real estate | 2002 |
| Aass Monsen Invest AS | | 2025 |
| AB Hage & Graveservice AS | Construction | 2009 |
| Abbl Eiendomsmegling AS | Real estate | 1983 |
| Accardo AS | Administrative & support | 2021 |
| Accelerate Invest AS | | 2018 |
| Acelerado AS | Information & communication | 2021 |
| Acharry-Invest AS | | 2020 |
| Ack Invest AS | Real estate | 2007 |
| Action Potential AS | Health & social care | 2013 |
| Activ Ski & Golf Ans | Wholesale & retail | 2001 |
| Adaptive AS | Information & communication | 2007 |
| Adiuvo AS | Information & communication | 1998 |
| Adventure Holding AS | Wholesale & retail | 2016 |
| Advokat Niels Kristian Axelsen AS | Professional & scientific | 2017 |
| Advokatfirma Christensen Friis-Møller Pettersson Da | Professional & scientific | 2005 |
| Advokatfirma Compliancepartner AS | Professional & scientific | 2013 |
| Advokatfirma Finne Lange AS | Professional & scientific | 2007 |
| Advokatfirma Friis-Møller AS | Professional & scientific | 2025 |
| Advokatfirma Lagata AS | Professional & scientific | 2020 |
| Advokatfirmaet Dehn Da | Professional & scientific | 2018 |
| Advokatfirmaet Jurilex AS | Professional & scientific | 2023 |
| Advokatfirmaet Tørresby Og Seegaard Dahlberg Ans | Professional & scientific | 1996 |
| Ae Drift AS | Real estate | 2023 |
| Agcy AS | Professional & scientific | 2024 |
| Aha Opplevelser AS | Administrative & support | 2015 |
| Aidevo AS | Information & communication | 2025 |
| Ajat Invest AS | | 2023 |
| Akademiet VGS Sandvika AS | Education | 2013 |
| Akershus Økonomi AS | Professional & scientific | 1989 |
| Akl Agri AS | Wholesale & retail | 2023 |
| Aklen AS | Professional & scientific | 2017 |
| Aktivt Renhold AS | Administrative & support | 1994 |
| Al Mahdi Bygg AS | Construction | 2026 |
| Alfheimr SA | Information & communication | 2015 |
| Algipharma AS | Professional & scientific | 1992 |
| Algipharma Holding AS | Manufacturing | 2017 |
| Alice Invest AS | Professional & scientific | 2022 |
| Aline Invest AS | | 2025 |
| Alruna AS | | 2020 |
| Amo Pharmacy AS | Health & social care | 2026 |
| Anax Investering AS | Financial services | 2004 |
| Ancha AS | Education | 2014 |
| Andenæs Eiendom AS | Real estate | 1986 |
| Andenæs Forvaltning AS | Real estate | 1988 |
| Andenæsgården Bekkestua AS | Real estate | 2017 |
| Andenæsgårdene Bærum AS | Real estate | 1986 |
| Anders Hovde AS | Construction | 2013 |
| Anima Dyreklinikk Og Butikk AS | Professional & scientific | 2004 |
| Anima Rehabilitering AS | Health & social care | 2012 |
| Anmaso AS | Professional & scientific | 2016 |
| Anna Thai Massasje AS | Other services | 2018 |
| Apla AS | Health & social care | 2022 |
| Apla Helse AS | Health & social care | 2021 |
| Apotek Sandvika Vest AS | Wholesale & retail | 2009 |
| Aprimo Analyse AS | Information & communication | 2024 |
| Aprimo Rådgivning AS | Administrative & support | 2008 |
| Aprimo Rådgivning Frode Semb AS | Professional & scientific | 2008 |
| Aprimo Rådgivning Jakob Digranes AS | Professional & scientific | 2022 |
| Aprimo Rådgivning Tor Hernæs AS | Professional & scientific | 2008 |
| Arena Markedsføring AS | Professional & scientific | 2024 |
| Ariba Eiendom AS | Real estate | 2019 |
| ARK1 Consulting AS | Professional & scientific | 2010 |
| Art AS | Professional & scientific | 2005 |
| Artefact Consulting AS | | 2019 |
| Artur Holding AS | | 2023 |
| Arvani Sound AS | Wholesale & retail | 2007 |
| Arygh Holding AS | | 2023 |
| AS Boreas | | 1957 |
| AS Bull Industri- Og Skipsteknisk | Wholesale & retail | 1980 |
| AS Bygdø Allé 73 | Households | 1932 |
| AS Clay I | Real estate | 1987 |
| AS Elisenbergveien 35 | Households | 1932 |
| AS Hamang Papirfabrik | Real estate | 2015 |
| AS Rodeløkkens Maskinverksted & Jernstøperi | Real estate | 1914 |
| AS Sportsartikler | Financial services | 1965 |
| AS Vivo | Real estate | 1940 |
| Asec Eiendom AS | Real estate | 1985 |
| Asker & Bærum Eiendomsdrift AS | Construction | 2017 |
| Asker Eiendom AS | Real estate | 1990 |
| Asker Og Bærum Steinimport AS | Wholesale & retail | 2017 |
| Asker Og Bærum Tannklinikk Sandvika AS | Health & social care | 2018 |
| Asker Og Bærums Budstikke AS | Information & communication | 2019 |
| Aspestrand AS | Real estate | 2009 |
| Asplan Viak AS | Professional & scientific | 1964 |
| Atechnic AS | Wholesale & retail | 2018 |
| Athr Academy AS | Education | 2025 |
| Attba AS | | 2024 |
| Aurora a AS | | 2018 |
| Auto Bærum AS | Wholesale & retail | 2017 |
| Auto Bærum Holding AS | Real estate | 2017 |
| Autopia Expo Trondheim AS | Administrative & support | 2022 |
| Autoyard AS | Wholesale & retail | 2021 |
| Avgrunnsdalen Holding AS | Professional & scientific | 2025 |