| Hano Holding AS | Professional & scientific | 2013 |
| Hansen & Dahl AS | Construction | 2001 |
| Hansen & Jensen Transport AS | Transport & logistics | 1999 |
| Hansen Transport & Service AS | Transport & logistics | 2018 |
| Hansoa AS | Health & social care | 2007 |
| Harald Og Bjørn Eiendom AS | Real estate | 2012 |
| Harridsleff Bygg & Eiendom AS | Professional & scientific | 2016 |
| Haslum Invest AS | Real estate | 2005 |
| Hasselbakken Holding AS | Real estate | 2005 |
| Havino AS | Information & communication | 2020 |
| Havnekroa AS | Hospitality | 2023 |
| HBS 1969 AS | Wholesale & retail | 2014 |
| HC Reservoir Engineering AS | Professional & scientific | 2005 |
| Heatmed Sport & Medical Care AS | Wholesale & retail | 2003 |
| Heavy Haulage Norway AS | Transport & logistics | 2024 |
| Hedvig Holding AS | | 2021 |
| Heimgård Eiendom AS | Real estate | 2016 |
| Heimo-Koru OY | Wholesale & retail | 1998 |
| Helge R Olsen Spedisjon AS | Transport & logistics | 2021 |
| Helge Stumberg AS | Construction | 2005 |
| Helge Stumberg Eiendom AS | Real estate | 2017 |
| Heli-Hansen Invest AS | Financial services | 2016 |
| Hellberg & Bjerkeli AS | Construction | 1983 |
| Hellboys Strongman Norway Da | Education | 2006 |
| Helle & Skogli Eiendom Ans | Real estate | 1996 |
| Helse Håpet AS | Health & social care | 2016 |
| Henr Køhn AS | Wholesale & retail | 1988 |
| Henrik Berger Holding AS | Information & communication | 2020 |
| Herføl Vann Og Avløp SA | Water & waste | 2003 |
| Herrebrøden AS | Construction | 2008 |
| Herrebrøden Gård AS | Wholesale & retail | 2018 |
| Hesse Holding AS | | 2023 |
| HH Investment AS | Wholesale & retail | 2004 |
| HH Prosjekt AS | Real estate | 2019 |
| Hiky AS | Financial services | 2009 |
| Hitsville Production AS | Information & communication | 1999 |
| Hitsville Tunes AB | Information & communication | 2004 |
| HKP Eiendom Holding AS | Real estate | 2015 |
| HMP Invest AS | Real estate | 2005 |
| Hokus Pokus Invest AS | | 2022 |
| Hollungen Vest Vann-Og Avløpslag SA | Water & waste | 2010 |
| Holmbo Eiendom AS | Real estate | 2017 |
| Holmsbo Holding AS | Financial services | 2006 |
| Hos Oss Halden AS | Wholesale & retail | 2025 |
| Hotelldrift Halden AS | Hospitality | 2006 |
| Hotelldrift Park Halden AS | Hospitality | 2014 |
| Hovelsen AS | Manufacturing | 2014 |
| Hovsveien 3 AS | Real estate | 2013 |
| Hovsveien Fus Barnehage AS | Education | 2018 |
| HP Halden AS | Real estate | 2023 |
| HP Halden Pharma AS | Manufacturing | 2023 |
| HPG AS | | 2021 |
| HRG AS | Professional & scientific | 2007 |
| Hsb-Øb Holding AS | | 2026 |
| HT Gjerder Østfold Og Akershus AS | Construction | 2018 |
| Hudlegekontoret I Halden AS | Health & social care | 2017 |
| Human Centred Design AS | Professional & scientific | 2018 |
| Hus Service AS | Construction | 2024 |
| Hvalen Eiendom AS | Real estate | 2013 |
| Hybridtech Fjeld Solkraftverk AS | Energy | 2009 |
| Hybridtech Prosjekter AS | Energy | 2024 |
| Hybridtech Renewables AS | Professional & scientific | 2024 |
| Hytte- Og Eiendomservice AS | Administrative & support | 2020 |
| Hyttebygg AS | Real estate | 2008 |
| Hårgleder AS | Other services | 2019 |
| Håvard Kristiansen Holding AS | | 2022 |
| Hør Meg AS | Education | 2024 |
| Høvik Bil AS | Wholesale & retail | 2022 |
| Høvik Grus Og Anlegg AS | Construction | 2010 |
| Høvik Kapital AS | | 2026 |
| Høvleriet Barnehage AS | Education | 2012 |
| Icli Norway AS | Professional & scientific | 2026 |
| Idd Bygdehus SA | Real estate | 2012 |
| Idd Eiendom AS | Real estate | 2010 |
| IDDEVEIEN41 AS | Construction | 2016 |
| Idrt AS | Professional & scientific | 2025 |
| Iel Holding AS | | 2022 |
| Iftec AS | Information & communication | 2026 |
| Il Casolare Halden AS | Hospitality | 2023 |
| Im-Holding AS | Real estate | 2005 |
| Immortal Ink AS | Other services | 2015 |
| Industrielt Produksjonsverktøy AS | Real estate | 2001 |
| Industriselskapet Grønland AS | Real estate | 1997 |
| Infox AS | Information & communication | 2026 |
| Ing Norsted AS | Real estate | 1997 |
| Inger Maries Cafe Da | Hospitality | 2002 |
| Ingerfjellveien AS | Real estate | 2008 |
| Ingierveien 6 Eiendom AS | Real estate | 1997 |
| Ingo AS | Financial services | 2002 |
| Inission Halden AS | Manufacturing | 2006 |
| Inkludio AS | Information & communication | 2026 |
| Innbolager Halden AS | Real estate | 2023 |
| Innholdsprodusenten AS | Information & communication | 2023 |
| Innrederiet AS | Wholesale & retail | 2021 |
| Innvikling AS | | 2022 |
| Inteq Group Norway AS | | 2026 |
| Inteq Solutions AS | Information & communication | 2026 |
| Inter Act AS | Real estate | 1997 |
| Inter-Data AS | Professional & scientific | 1969 |
| Interior Direct Nuf | Wholesale & retail | 2008 |