| Hyr Helgeland AS | Administrative & support | 2026 |
| Håli Holding AS | Real estate | 2005 |
| Ifo Invest AS | | 2025 |
| Ihip AS | Hospitality | 2021 |
| III AS | | 2026 |
| Ik-Utleie Da | Administrative & support | 2008 |
| Industrirenhold AS | Administrative & support | 2018 |
| Industrivegen 10 Eiendom AS | Real estate | 2012 |
| Ingebrigtsen Næringseiendom AS | Real estate | 2016 |
| Ingeniør Rune AS | Professional & scientific | 2012 |
| Ingeniør Terje Jakobsen AS | Professional & scientific | 1998 |
| Inord Regnskap AS | Professional & scientific | 2024 |
| Inri AS | Administrative & support | 2024 |
| Inspekt Molab AS | Professional & scientific | 2023 |
| Inspekt Norway AS | Professional & scientific | 2023 |
| Intakt Bilskade Helgeland AS | Other services | 1982 |
| Interiør Galleriet AS | Manufacturing | 2011 |
| Intersport Mosjøen AS | Wholesale & retail | 2005 |
| Inventit AS | | 2015 |
| Invests AS | | 2026 |
| IT Jan Erik Johansen AS | Information & communication | 2013 |
| J Eberg Hansen AS | Construction | 1984 |
| J. L. Trading AS | | 2025 |
| J. Pedersen Bygg AS | Construction | 2020 |
| Ja Takk Kontor AS | Wholesale & retail | 1998 |
| Jahbygg Norge AS | Construction | 2026 |
| Jahbygg Oü Nuf | Construction | 2012 |
| Jan Kjønnås AS | Administrative & support | 2007 |
| Jan Kjønnås Eiendom AS | Real estate | 2008 |
| Janto Eiendom AS | Real estate | 2001 |
| Jap Eiendom AS | Real estate | 2015 |
| Jc-Holding AS | | 2024 |
| Jefo Holding AS | Real estate | 2013 |
| Jessen United AS | Professional & scientific | 2021 |
| Jiha Holding AS | Health & social care | 2022 |
| JKK Maskin AS | Construction | 2013 |
| JMJ AS | | 2026 |
| Joeni AS | Professional & scientific | 2018 |
| Johansen & Co AS | Administrative & support | 2014 |
| Johnny Larsen AS | Construction | 1995 |
| Jomai Eiendom AS | Real estate | 2013 |
| Jordmorhuset AS | Health & social care | 2016 |
| Jorem Eiendom AS | Real estate | 2005 |
| JR Drift Og Vedlikehold AS | Construction | 2020 |
| JT Golf AS | Wholesale & retail | 2023 |
| Juwike Invest AS | | 2025 |
| Jæft AS | Wholesale & retail | 2017 |
| Jørgensen Eiendom Nord AS | Real estate | 2017 |
| K.H Al-Alahmad AS | Hospitality | 2023 |
| Kallax Flyg AS | Transport & logistics | 2014 |
| Kamaca Invest AS | Financial services | 2011 |
| Kastnes Holding AS | Real estate | 2015 |
| Kato Holding AS | Real estate | 2010 |
| Keje Holding AS | | 2023 |
| Kilværbryggene Fritidseiendom AS | Real estate | 1997 |
| Kippermoen Friluftsbarnehage AS | Education | 2007 |
| Kirkegata 22 AS | Real estate | 2010 |
| Kirkegata Eiendom Mosjøen AS | Real estate | 2015 |
| Kirsti Stokland AS | Arts & recreation | 2014 |
| Kjeberget Holding AS | Administrative & support | 2024 |
| Kjemsås Maskinstasjon Ans | Construction | 1989 |
| Kjeveortopedisk Klinikk AS | Health & social care | 2022 |
| Kjøløymo Holding AS | Wholesale & retail | 2023 |
| Kjøpeselge AS | Information & communication | 2025 |
| Kleppen Massetak AS | Mining & quarrying | 2017 |
| Klokkeren AS | Wholesale & retail | 2013 |
| Kmo Holding AS | | 2005 |
| Knøttene AS | Wholesale & retail | 1996 |
| Kolbjørn Nilsskog AS | Construction | 1995 |
| Konsulent Steinar Stien AS | Agriculture & fishing | 2025 |
| Kremmerhuset Ans | Wholesale & retail | 1991 |
| Kress AS | Hospitality | 2020 |
| Krimax AS | Wholesale & retail | 2010 |
| Kroverten Mosjøen AS | Hospitality | 2001 |
| Krute Kåk AS | Hospitality | 2021 |
| Kulturverkstedet AS | Hospitality | 2012 |
| Kvigtind Holding AS | Real estate | 2005 |
| Kvikk Eiendom Mosjøen AS | Real estate | 2008 |
| Kvikk Service AS | Administrative & support | 1996 |
| KWH Invest AS | Arts & recreation | 2005 |
| L.G. Eiendom AS | Real estate | 2018 |
| Labakken Invest AS | Real estate | 2004 |
| Lagmannsgata 16 AS | Real estate | 2018 |
| Laksforsmo Holding AS | Administrative & support | 2021 |
| Laksforsmo Service AS | Administrative & support | 2013 |
| Lama Invest AS | Administrative & support | 1995 |
| Lamax Invest AS | Financial services | 2014 |
| Landbruksskolens Barnehage SA | Education | 1989 |
| Lars Farbu AS | Professional & scientific | 2012 |
| Lars Roger Olsen Transport AS | Transport & logistics | 2009 |
| Latoro Eiendom AS | Real estate | 2021 |
| Legato AS | Real estate | 1991 |
| Legax AS | Real estate | 2022 |
| Leif Villy Svendsen AS | Transport & logistics | 2009 |
| Leira 20 AS | Wholesale & retail | 2018 |
| Leiro Eiendom AS | Real estate | 2025 |
| Lekebutikken Mosjøen AS | Wholesale & retail | 1998 |
| Lensegata 8-10 AS | Real estate | 2021 |
| Lensegata Eiendom AS | Real estate | 2012 |
| Linea AS | Energy | 2016 |