| 12 Punkt Kommunikasjonsdesign AS | Professional & scientific | 2012 |
| 22 Invest AS | Real estate | 2020 |
| 3 - Hus Follo AS | Real estate | 2006 |
| 360 Logistics AS | Administrative & support | 2018 |
| 360 Logistics Holding AS | Administrative & support | 2018 |
| 4C Invest AS | Professional & scientific | 2017 |
| 4DIALOG AS | Information & communication | 2009 |
| A Kaur Concept AS | Professional & scientific | 2026 |
| A-Bygg AS | Professional & scientific | 1982 |
| A.I.Vent AS | Construction | 2012 |
| A.L Holding AS | Other services | 2021 |
| A.S.I.E AS | | 2023 |
| A1 Living AS | Real estate | 2020 |
| A3T Invest AS | Professional & scientific | 2008 |
| Aamodt Fysikalske Institutt Og Treningssenter AS | Health & social care | 2013 |
| Aamodt Fysioterapi AS | Health & social care | 2019 |
| Aasheimgaarden AS | Hospitality | 2026 |
| Ab-M AS | Wholesale & retail | 1990 |
| Abekon AS | Professional & scientific | 2018 |
| Abga Invest AS | | 2026 |
| Ac Videoproduksjon Da Ødegård Og Ringstad | Information & communication | 1989 |
| Accanto AS | | 2021 |
| Activesport AS | Wholesale & retail | 2012 |
| Ada Bygg AS | Construction | 2026 |
| Adaggio Hov AS | Arts & recreation | 2015 |
| Adel Holding AS | | 2005 |
| Adelaide AS | | 2025 |
| Advokat Erling Høyte AS | Professional & scientific | 2020 |
| Advokat Gro Arnesen Fremstad AS | Professional & scientific | 2016 |
| Advokat Håvar Wiik AS | Professional & scientific | 2011 |
| Advokat Ingrid Høyte AS | Professional & scientific | 2023 |
| Advokat Lene Frykman AS | Professional & scientific | 2006 |
| Advokatfirmaet Oscar Ihlebæk AS | Professional & scientific | 1989 |
| Aedifi AS | Professional & scientific | 2022 |
| Afro Invest AS | Professional & scientific | 2017 |
| Afrodites Skjønnhet AS | Other services | 2015 |
| AI Accounting AS | Administrative & support | 2016 |
| Akbk Invest AS | Real estate | 2020 |
| Akershus Amtstidende AS | Information & communication | 1982 |
| Akershus Miljø AS | Water & waste | 2014 |
| Aksima Psykologtjenester AS | Health & social care | 2022 |
| Akutt Eiendom AS | Real estate | 2006 |
| Aladdin Drøbak AS | Wholesale & retail | 2026 |
| Albion Holding AS | Wholesale & retail | 2021 |
| Alcuni Trading AS | Professional & scientific | 2010 |
| Alden Invest AS | Real estate | 2006 |
| Alexis Mote AS | Wholesale & retail | 2007 |
| Alicenborg Boligutvikling AS | Real estate | 2019 |
| Alicja Renhold AS | Administrative & support | 2023 |
| All Digital AS | Information & communication | 2013 |
| Alliance Healthcare Norge AS | Wholesale & retail | 1971 |
| Allimak Invest AS | Financial services | 2015 |
| Alm Holding AS | Real estate | 2005 |
| Alos Holding AS | | 2022 |
| Alt Innen Elektro Oslo AS | Construction | 2021 |
| Ammacks AS | Real estate | 2005 |
| Amos & Co AS | | 2021 |
| Ananta Balance AS | Education | 2025 |
| Anbak Holding AS | Real estate | 2019 |
| Andel Holding AS | Real estate | 2020 |
| Anders & Far Invest AS | Financial services | 2005 |
| Andkon Invest AS | | 2019 |
| Andretti Rapido AS | | 2021 |
| Ane Services AS | | 2018 |
| Anidei AS | Real estate | 2014 |
| Anima AS | Health & social care | 1989 |
| Anker Drift AS | Wholesale & retail | 2023 |
| Anker Eiendommer AS | Real estate | 2024 |
| Anker Restaurant Drift AS | Hospitality | 2026 |
| Anleggsgartner Sigurd Johannessen AS | Administrative & support | 2015 |
| Ann Helen Frisør AS | Other services | 2021 |
| Anna Storbraaten AS | Professional & scientific | 2020 |
| Annabeth AS | | 2010 |
| Anne Elisabeth Thurmann Invest AS | Health & social care | 2025 |
| Anne Grete Preus Fondet AS | Administrative & support | 2021 |
| Anneks Drøbak AS | Wholesale & retail | 2010 |
| Annikas Hårdesign AS | Other services | 2012 |
| Antares Consulting | Information & communication | 2014 |
| Antineutrino AS | Financial services | 2018 |
| Appelsin AS | Information & communication | 2021 |
| Appoteket AS | Wholesale & retail | 2023 |
| Aquasafe Da | Arts & recreation | 1996 |
| Arborconsult AS | Professional & scientific | 2020 |
| Archnetic Labs AS | Information & communication | 2026 |
| Arden Greentech & Wealth AS | Professional & scientific | 2022 |
| Argus Vakt Og Alarm Da | Construction | 1993 |
| Arkitekt Mats Bjørklund AS | Real estate | 1993 |
| Arkitektpartner AS | Professional & scientific | 1993 |
| Arkitekturbygg AS | Professional & scientific | 2010 |
| Arkivconsult AS | Information & communication | 2017 |
| Arleon Holding AS | | 2026 |
| Arne Frostad Holding AS | Real estate | 2007 |
| Arne Mjøsund AS | Wholesale & retail | 2008 |
| Artha Helseconsult AS | Health & social care | 1996 |
| Artha Helseconsult Da | Health & social care | 2000 |
| AS Auto Askim Interim | Wholesale & retail | 2021 |
| AS Frogn Bilverksted | Real estate | 1965 |
| AS Kirkegaten 9 | Real estate | 1969 |
| AS Lambeth & Co | Real estate | 2021 |
| Asbj W Christophersen & Co AS | Transport & logistics | 1941 |