| Interiørbutikken Nina AS | Wholesale & retail | 2014 |
| Intersport Halden AS | Wholesale & retail | 2021 |
| Inves Holding AS | Real estate | 2025 |
| Invest Hus AS | Real estate | 2017 |
| Iog Holding AS | Financial services | 2014 |
| Ipco AS | Information & communication | 2019 |
| Irpa AS | Professional & scientific | 2013 |
| Isebakkeveien 49 AS | Real estate | 2013 |
| Isebakkeveien 50 AS | Real estate | 2000 |
| Isebakkeveien 55 AS | Real estate | 2005 |
| Isebakkeveien 75 AS | Real estate | 2013 |
| Ivar Sæter AS | Wholesale & retail | 1970 |
| Iversen Transport Og Consult AS | Transport & logistics | 2016 |
| Iversens Mekaniske AS | Manufacturing | 1975 |
| J O Trading AS | Construction | 1988 |
| J S Madsen AS | Education | 2025 |
| J.I Håndverk Service AS | Construction | 2025 |
| Ja Kristiansen AS | Financial services | 2013 |
| Jacta Eiendom AS | Hospitality | 2010 |
| Jan Andersen & Sønn AS Bygg Og Tømrermester | Construction | 1991 |
| Jan Erik Johnsen AS | Wholesale & retail | 2005 |
| Jan-Rune Nilsen Holding AS | | 2006 |
| Jarle Og Marie Herrebrøden Ans | Agriculture & fishing | 2020 |
| Jensen & Lund Da | Real estate | 1989 |
| Jensen & Lunds Billakkeringsverksted Da | Other services | 1999 |
| Jensen & Scheele AS | Real estate | 2018 |
| Jensen Og Scheele Eiendom AS | Real estate | 1997 |
| Jerkyshop.No AS | Wholesale & retail | 2022 |
| Jesper Skorpen AS | Information & communication | 2022 |
| Jetcarrier AS | Transport & logistics | 2019 |
| Jetcarrier Logistics AS | Transport & logistics | 2000 |
| Jetcarrier Solutions AS | Transport & logistics | 2011 |
| Jik Invest AS | Financial services | 2001 |
| Jlauritzen AS | Real estate | 2025 |
| JML Eiendom AS | Professional & scientific | 2016 |
| Jo Fog Och Lim Konsult AB | Professional & scientific | 2017 |
| Johan Lauritzen AS | Manufacturing | 2024 |
| Johander Internationell Transport AB | Transport & logistics | 2006 |
| Johns Bygg & Fasad AB | Professional & scientific | 2007 |
| Johnsen Invest AS | Real estate | 1999 |
| Joli AS | Professional & scientific | 2005 |
| Joll Holding AS | Real estate | 2020 |
| Jolo Holding AS | | 2023 |
| Jon Barons Fiskeutstyr AS | Wholesale & retail | 2020 |
| Jon Myhre AS | Wholesale & retail | 2014 |
| Jonabo AS | Information & communication | 2011 |
| Jordbærpikene Tista AS | Hospitality | 2023 |
| Josefinesgt 25 AS | Real estate | 2004 |
| JR Entreprenør AS | Construction | 2023 |
| JS Eiendom Invest AS | Administrative & support | 2009 |
| JTC Auto AS | Wholesale & retail | 2016 |
| Jumo Norway AS | Wholesale & retail | 2002 |
| Jva Eiendomsutvikling AS | Real estate | 1998 |
| Jva Holding AS | Real estate | 2005 |
| JVP Holding AS | Construction | 2020 |
| Järnheimr AS | Wholesale & retail | 2024 |
| Järnheimr Holding AS | | 2025 |
| Jøkeltun AS | | 2023 |
| K & B Eiendom AS | Real estate | 2011 |
| Ka Eriksen Invest AS | Wholesale & retail | 2005 |
| Kai Marketing AS | Information & communication | 2020 |
| Kalibo AS | Wholesale & retail | 2010 |
| Kalnes Helsepark AS | | 2026 |
| Kalnes Helsepark Tomt AS | Real estate | 2026 |
| Kandusi AS | Information & communication | 2015 |
| Kaniya Eiendom AS | Real estate | 2015 |
| Kaniya Holding AS | Hospitality | 2015 |
| Kapabel Helseklinikk AS | Health & social care | 2022 |
| Kar Invest AS | Administrative & support | 2002 |
| Karlsborg Invest AS | Wholesale & retail | 2019 |
| Karlsen Og Solberg Da | Construction | 2007 |
| Karrestad Eiendom AS | Real estate | 2020 |
| Karrestad Legesenter Ans | Health & social care | 2003 |
| Karrestad Legesenter AS | Health & social care | 2022 |
| Kartopap Converting AS | Wholesale & retail | 2009 |
| Kauguri AS | Construction | 2012 |
| KBM Gruppen AS | Wholesale & retail | 2017 |
| KC Group AS | Wholesale & retail | 2024 |
| Kebab Corner AS | Hospitality | 2020 |
| Kebab House 1 AS | Hospitality | 2021 |
| Kebab Pizza House 4 Halden AS | Hospitality | 2020 |
| Kebabfabrikken Halden AS | Hospitality | 2025 |
| Kega Holding AS | Wholesale & retail | 2020 |
| Kennel Workingpearl Da | Agriculture & fishing | 2023 |
| Kerberos Investment AS | Real estate | 2011 |
| Ketilka AS | | 2005 |
| Kevaglen AS | Professional & scientific | 2026 |
| Keygard AS | Wholesale & retail | 2023 |
| KG Motor AS | Wholesale & retail | 2015 |
| KG Records AS | Arts & recreation | 2022 |
| Khan Eiendom AS | Real estate | 2026 |
| Kiellandsgate Eiendom AS | Real estate | 2013 |
| Kildebo Blomster AS | Wholesale & retail | 2004 |
| Kinoguiden Invest Ans | Information & communication | 2000 |
| Kirkeborg AS | Real estate | 2006 |
| Kiropraktor Ann-Kristin Brodin AS | Health & social care | 2020 |
| Kiropraktorkontoret Brodin & Ohlgren Tidemann AS | Health & social care | 2022 |
| Kitemaker AS | Information & communication | 2019 |
| Kitemaker Holding AS | | 2020 |
| Kjell-Inge Dahlbom Murartjänst | Construction | 1998 |