| BCJ AS | Administrative & support | 2022 |
| Beauty Invest AS | Other services | 2024 |
| Bednar Invest AS | | 2025 |
| Beki Holding AS | Real estate | 2024 |
| Beleven AS | | 2024 |
| Beleven Produksjoner AS | Arts & recreation | 2020 |
| Benchmark Accounting AS | Professional & scientific | 2023 |
| Benchmark Performance AS | Professional & scientific | 2019 |
| Bengt Eriksen Holding AS | | 2020 |
| Benny Travel Ltd Nuf | Administrative & support | 2004 |
| Benthol AS | | 2025 |
| Beo-Grafisk AS | Manufacturing | 1998 |
| Berby AS | Real estate | 2017 |
| Berg Innovation AS | Professional & scientific | 2006 |
| Berg Prosjekt AS | Real estate | 1986 |
| Berger Næring AS | Real estate | 1996 |
| Berget Utbygging AS | Real estate | 2018 |
| Bergheim Snøservice AS | Administrative & support | 2008 |
| Bergingstjenester AS | Transport & logistics | 2019 |
| Bergsløkken Holding AS | | 2026 |
| Bergsløkken Management AS | Professional & scientific | 2020 |
| Bergvill Eiendom AS | Real estate | 2023 |
| Berivan Frisør AS | Other services | 2012 |
| Bern AS | Professional & scientific | 1994 |
| Betalingsgaranti AS | Administrative & support | 2015 |
| Betonmast Romerike AS | Construction | 2009 |
| Beyond Kommunikasjon AS | Professional & scientific | 2016 |
| Bico Bil AS | Administrative & support | 2002 |
| Big Biff Lillestrøm AS | Hospitality | 2007 |
| Big Tuna Holding Company AS | Real estate | 2015 |
| Bil for Alle AS | Wholesale & retail | 2021 |
| Bilnå AS | Administrative & support | 2026 |
| Bilservice Lillestrøm AS | Other services | 2016 |
| Bilvask Express AS | Other services | 2013 |
| Bingoo AS | Arts & recreation | 2018 |
| Biolsi AS | | 2021 |
| Bit Holding AS | | 2021 |
| Bite-Tech Dataservice AS | Wholesale & retail | 1990 |
| Bjerke & Andresen AS | Other services | 2012 |
| Bjerkealleen 26 AS | Real estate | 1974 |
| Bjerkelivegen 7 AS | Real estate | 2021 |
| BJL Invest AS | | 2005 |
| Bjorlyen AS | | 2023 |
| Bjørkum Bolig AS | Real estate | 2019 |
| Bjørkum Investment AS | Real estate | 2021 |
| Bjørn Erik Løvlien AS | Construction | 2000 |
| Bjørn Olaussen AS | Real estate | 2005 |
| Bjørnar Torsnes AS | Information & communication | 2005 |
| Bjørnholthagan AS | Real estate | 2020 |
| Bjørnm AS | | 2025 |
| Bjørnsonsgt 34 AS | Real estate | 1991 |
| BKS AS | Professional & scientific | 2008 |
| Black Sheep Investment AS | | 2023 |
| Blaker Bygdeservice SA | Administrative & support | 1992 |
| Blix Kapital AS | | 2026 |
| Blomhoff Holding AS | | 2025 |
| Blue Phoenix Norway AS | Water & waste | 2016 |
| Blue Skies Aero AS | Professional & scientific | 2015 |
| BN Gruppen AS | Professional & scientific | 2009 |
| BNB Ventures AS | Professional & scientific | 2024 |
| Boko AS | Real estate | 2015 |
| Boligbanken ASA | Financial services | 2014 |
| Boligbyggelagenes Fritidsboliger AS | Wholesale & retail | 2003 |
| Bolstad Engesvoll Consult Da | Professional & scientific | 2012 |
| Bookdragons AS | Wholesale & retail | 2024 |
| Bookeriet AS | Professional & scientific | 2026 |
| Boppus Invest AS | Real estate | 2016 |
| Borg Hydrogen AS | Energy | 2023 |
| Borgengården AS | Real estate | 2017 |
| Bori Timbre AS | Real estate | 2025 |
| Bori Utbygging AS | Real estate | 1995 |
| Bori Utleieforvaltning AS | Real estate | 2015 |
| Bori Utleiemegler AS | Real estate | 2015 |
| Bottenvik AS | Administrative & support | 2012 |
| Bragdur AS | Professional & scientific | 2020 |
| Brak Invest AS | Real estate | 2020 |
| Brandarc AS | | 2021 |
| Branderud Holding AS | | 2026 |
| Brandsdal Studio AS | Professional & scientific | 2019 |
| Brandvoldgata 2 Og 4 AS | Real estate | 2016 |
| Brass & Treblås AS | Wholesale & retail | 1992 |
| Bratlie Bygg AS | Construction | 2014 |
| Bray Holding AS | Financial services | 2018 |
| Bredal Maskin AS | Construction | 2024 |
| Bredde Invest AS | Real estate | 2001 |
| Brico Eiendom AS | Real estate | 2008 |
| Brotnow Ans | Education | 2002 |
| Brubak Consulting AS | Information & communication | 2010 |
| Brynsen Holding AS | Information & communication | 2025 |
| Brådalsstubben 1-3 AS | Real estate | 2005 |
| Brürius Ventures AS | Professional & scientific | 2019 |
| BTC Bygg AS | Construction | 2016 |
| Bto Konsulenten AS | Arts & recreation | 2018 |
| Bullo AS | Real estate | 2015 |
| Burgertralla Øst AS | Hospitality | 2020 |
| Business Lillestrøm AS | Professional & scientific | 2014 |
| Businessformidling AS | Professional & scientific | 1997 |
| Butikkdrift Ditu AS | Wholesale & retail | 2021 |
| Butikkdrift Olaru AS | Wholesale & retail | 2023 |
| Butikkdrift Øyvind Hirkjølen AS | Wholesale & retail | 2013 |