| Borgerskansen Invest AS | | 2021 |
| Borring Holding AS | Real estate | 2019 |
| Bosa Retail AS | Wholesale & retail | 2022 |
| Boverket AS | Professional & scientific | 2005 |
| Bpa Drift AS | Health & social care | 2006 |
| BR Pedersen AS | Construction | 2002 |
| BR Pedersen Utvikling AS | Real estate | 2015 |
| Bra-Bo AS | Real estate | 1995 |
| Braadlands Mekaniske AS | Manufacturing | 2026 |
| Brady Energy Norway AS | Information & communication | 2003 |
| Brannberget Holding AS | Financial services | 2012 |
| Bratbakken/Karlsen Holding AS | Construction | 2024 |
| Bratech AS | Wholesale & retail | 2025 |
| Brattli Takst Og Byggvurdering AS | Real estate | 2008 |
| Brattås Eiendom AS | Real estate | 2019 |
| Brattås Halden AS | Real estate | 2015 |
| Brattåstunet Bolig AS | Real estate | 2021 |
| Breda Holding AS | | 2023 |
| Brekke Stenbrudd Nuf | Mining & quarrying | 2006 |
| BRH 2 Invest AS | Real estate | 2018 |
| BRM Holding AS | Real estate | 2014 |
| Bryggekanten Restaurant AS | Hospitality | 2016 |
| Bråthen R&R AS | Professional & scientific | 2020 |
| Brød & Vann AS | Manufacturing | 2013 |
| Brød & Vann Halden AS | Manufacturing | 2021 |
| Brødenveien Avløpslag | Construction | 2013 |
| Brødenveien Avløpslag SA | Water & waste | 2013 |
| Brødløs Bakeriutsalg AS | Wholesale & retail | 2017 |
| Brødløs Energi AS | Wholesale & retail | 2025 |
| Brødr Hansen Maskindrift AS | Construction | 1998 |
| Brødrene Coldbeersen AS | Wholesale & retail | 2023 |
| Brødrene Eriksen Eiendom AS | Real estate | 2004 |
| Brødrene Hammershaug AS | Construction | 2023 |
| Btbs AS | Wholesale & retail | 2017 |
| BTH Eiendom II AS | Wholesale & retail | 2007 |
| BTH Holding AS | Wholesale & retail | 2005 |
| Btøh AS | Wholesale & retail | 2017 |
| Bud-Bau Stillas AS | Construction | 2013 |
| Budo Sport-Drop in AS | Other services | 1998 |
| Buer & Stenersrød Vann Og Avløp SA | Water & waste | 2013 |
| Buerfeltet Vann Og Avløp SA | Water & waste | 2020 |
| Buermade AS | Construction | 2023 |
| Bukholm Holding AS | | 2021 |
| Bustadhus AS | Construction | 2016 |
| Butts Bistro & Tandoori AS | Hospitality | 1997 |
| Bygdeborg Invest AS | Construction | 2000 |
| Bygdeservice Norge SA | Other services | 2002 |
| Byggentreprenør Halden AS | Construction | 2022 |
| Byggfirma Lintho Og Skogli AS | Construction | 2015 |
| Byggmester Bjerkeli Eiendom AS | Real estate | 2016 |
| Byggmester Bjørn Larsen Eftf. AS | Construction | 2010 |
| Byggmester Bokerød AS | Construction | 2024 |
| Byggmester David Kitterød AS | Construction | 2024 |
| Byggmester Falch-Pedersen AS | Construction | 2019 |
| Byggmester Magne Holt AS | Construction | 2013 |
| Byggmester Roer AS | Construction | 2002 |
| Byggmester Tommy Lund AS | Construction | 2020 |
| Byggmiljø AS | Professional & scientific | 2002 |
| Brødr Damgaard ANS | Construction | 1988 |
| Båt-Holm AS | Wholesale & retail | 1987 |
| Bækhus Eiendom AS | Real estate | 2025 |
| Börjes Tingsryd AB Nuf | Wholesale & retail | 2004 |
| Børre Goplen AS | Real estate | 1997 |
| C N Snickerier | Wholesale & retail | 2007 |
| C-G Holding AS | Real estate | 2005 |
| C-G Invest AS | Real estate | 2007 |
| C. Norsted AS | Real estate | 2005 |
| C.E. Bøsterud AS | Professional & scientific | 2006 |
| C.Fredrik Holding AS | | 2021 |
| Caab Holding AS | | 2026 |
| Caiyan Wang AS | Professional & scientific | 2025 |
| Caleidoscope Systems AB | Construction | 2010 |
| Calmed Nuf | Wholesale & retail | 2008 |
| Camarosrock Ans | Arts & recreation | 2002 |
| Cambak Invest AS | | 2023 |
| Camel & Corduroy Da | Arts & recreation | 2024 |
| Campino Pizza House AS | Hospitality | 2012 |
| Campus Halden AS | Education | 2020 |
| Capable Tech AS | Health & social care | 2024 |
| Car Connect AS | Wholesale & retail | 2024 |
| Carcare.No AS | Other services | 2020 |
| Carro Sia | Transport & logistics | 2020 |
| Caso Holding AS | | 2024 |
| Caspersen Eiendom AS | Construction | 1992 |
| Cate Invest AS | | 2025 |
| Cato Ringstad AS | Manufacturing | 1975 |
| Cavern Stores AS | Wholesale & retail | 2023 |
| Cecilies Blomster AS | Wholesale & retail | 2004 |
| Cellbes AS | Wholesale & retail | 1995 |
| Centrum Legekontor Halden AS | Health & social care | 2008 |
| Cereb AS | Real estate | 2018 |
| Cews AS | Real estate | 2023 |
| Changthai AS | Other services | 2024 |
| Chargenode AS | Professional & scientific | 2022 |
| Charlou Invest AS | | 2026 |
| Chessgo AS | Manufacturing | 2024 |
| Chreng Holding AS | | 2021 |
| CK Boliger AS | Real estate | 2023 |
| Clean Burn Tech AS | Professional & scientific | 2023 |
| Clickz AS | Information & communication | 2022 |