| 1779 Holding AS | | 2023 |
| 1ESTÅENDE AS | Professional & scientific | 2023 |
| 24 Center AS | Administrative & support | 2021 |
| 7 Små Rom AS | Wholesale & retail | 2024 |
| 7-LUND Holding AS | | 2020 |
| A Bolig AS | Real estate | 2022 |
| A Madsen Holding AS | | 2021 |
| A'Vera AS | Wholesale & retail | 2007 |
| A-M-B Holding AS | Professional & scientific | 2008 |
| A.O.V.B Holding AS | | 2022 |
| Aabol Eiendom AS | Real estate | 2019 |
| Aarums Towing Service AS | Transport & logistics | 2017 |
| Aasekjær Miljøpark AS | Water & waste | 2022 |
| Aasgaard Holding AS | Financial services | 2014 |
| AB Fogspecialisten | Construction | 2009 |
| AB Halden AS | Information & communication | 2025 |
| Abc Eiendom AS | Real estate | 2004 |
| Abc Norsted AS | Real estate | 2005 |
| Abc Partner-Bygg AS | Construction | 2013 |
| Absoflex AB | Construction | 2001 |
| Absolute Bar AS | Hospitality | 1993 |
| Accline AB Nuf | Wholesale & retail | 2009 |
| Ace Trafikkskole AS | Education | 2024 |
| Acr Norway | Transport & logistics | 2016 |
| Adolesco AS | Wholesale & retail | 2012 |
| Advokat Hans Henrik Pettersen AS | Professional & scientific | 2003 |
| Advokatfirma Wang & Holm-Olsen AS | Professional & scientific | 2013 |
| Advokatfirmaet Parmer AS | Professional & scientific | 2013 |
| AG Foto AS | Wholesale & retail | 1987 |
| AI DC Norway AS | Construction | 2006 |
| Ainora AS | Information & communication | 2025 |
| Airecognise AS | Information & communication | 2020 |
| Airmont AS | Professional & scientific | 2019 |
| Aj Motors AS | Wholesale & retail | 2023 |
| Ajot Montering AS | Construction | 2016 |
| Akkynn AS | Professional & scientific | 2022 |
| Aktiv Halden AS | Real estate | 2003 |
| Aktivum AS | Arts & recreation | 1997 |
| Aladdin Scene AS | Arts & recreation | 2021 |
| Aladdin Wines AS | Wholesale & retail | 2024 |
| Aleksander Moen AS | Professional & scientific | 2013 |
| Alfheim Barnehage AS | Education | 1997 |
| Alfort & Cronholm AS | Wholesale & retail | 1999 |
| Alfredsson Tak AS | Construction | 2025 |
| Alk AS | Health & social care | 2019 |
| Alle Tiders Klær & Interiør AS | Wholesale & retail | 2023 |
| Allivara Ltd Nuf | Other services | 2022 |
| Allsang På Grensen AS | Arts & recreation | 2016 |
| Almawi AS | Information & communication | 2023 |
| Aloe Vera Cosmetics AS | Wholesale & retail | 1993 |
| Altibac Produkter AS | Wholesale & retail | 2020 |
| Altipack AS | Wholesale & retail | 1990 |
| Aluminiumsgården Eiendom AS | Real estate | 2019 |
| Ama Group AS | Wholesale & retail | 1988 |
| Amanda Strand AS | Administrative & support | 2024 |
| Ambient Lounge Norge AS | Wholesale & retail | 2016 |
| Amerikanske Bildeler AS | Wholesale & retail | 2004 |
| Amojso AS | | 2016 |
| Amt Eiendom AS | Real estate | 2003 |
| Amundsen Og Sørlie Ans | Real estate | 1987 |
| Amundsen Og Sørlie AS | Real estate | 2006 |
| Anders Frøberg | | 1996 |
| Andersen Og Berg Consult AS | Professional & scientific | 2019 |
| Andersen Økonomikonsult AS | Professional & scientific | 2004 |
| Andreas Andersen Holding AS | Wholesale & retail | 2010 |
| Ann-Charlotte Kristiansen AS | Other services | 2011 |
| Anne's Frisørstue AS | Other services | 2017 |
| Anne-Lene AS | Wholesale & retail | 2022 |
| Anne-Mette Andersen AS | Wholesale & retail | 2022 |
| Anneno Holding AS | | 2005 |
| Annes Jordmorstue AS | Health & social care | 2019 |
| Anonsen Eftf. AS | Manufacturing | 1991 |
| Anpela AS | Real estate | 2013 |
| Anthonio's Byggtjänst | Construction | 2004 |
| Applaus Kulturproduksjoner AS | Education | 2019 |
| Arabo Invest AS | Financial services | 1994 |
| Arborex AS | Agriculture & fishing | 2023 |
| Arctic Trade AS | Professional & scientific | 2025 |
| Arild Bjørn Og Simen Ans | Real estate | 1998 |
| Arken Eiendom AS | Real estate | 2022 |
| Arken Halden AS | | 2022 |
| Arnas Holding AS | Real estate | 2019 |
| Arnas Tilbud AS | Construction | 2015 |
| Arnas Tilbud Bygg AS | Construction | 2026 |
| Arnas Tilbud Flis AS | Construction | 2026 |
| Arnas Tilbud Maler AS | Construction | 2026 |
| Arnesen-Invest AS | Administrative & support | 2012 |
| Arnesens Eiendom AS | Real estate | 2024 |
| Arnesens Holding AS | Real estate | 2024 |
| Arnstad Invest AS | Financial services | 2005 |
| Aronsen Bygg Og Vedlikehold AS | Construction | 2012 |
| AS Den Norske Reiseeffektfabrik | Professional & scientific | 1898 |
| AS Halden Arbeiderblad | Information & communication | 1983 |
| AS Lundi | Professional & scientific | 1986 |
| AS Modesnitt | Real estate | 1982 |
| AS Storgaten 10 | Real estate | 1982 |
| Asak Eiendom AS | Real estate | 1988 |
| Asak Holding AS | Construction | 2005 |
| Asak Kulturbarnehage AS | Education | 2022 |
| Asak Prosjekt AS | Real estate | 2015 |