| Institutt for Skjematerapi AS | Education | 2014 |
| Interiørhuset Kongsvinger Ans | Wholesale & retail | 2000 |
| Introduction AS | Wholesale & retail | 2016 |
| Intus Exo AS | Wholesale & retail | 2025 |
| Isa Øiseth Holding AS | Real estate | 2017 |
| IT Øst AS | Information & communication | 2007 |
| ITCONSULT4U AS | Information & communication | 2015 |
| Iterativ AS | Information & communication | 2017 |
| Ivam AS | | 2023 |
| Ivar Hagen & Co Ans | Real estate | 1971 |
| Ivbk Rør AS | Construction | 2024 |
| J E Kristoffersen Eiendom AS | Wholesale & retail | 1990 |
| J-Eiendom AS | Real estate | 1990 |
| Jahnsrud AS | Wholesale & retail | 2021 |
| Jahnsrud Eiendom AS | Real estate | 2021 |
| Jbe Invest AS | Wholesale & retail | 2022 |
| Je Ma Casino & Partyservice Aktiebolag | Transport & logistics | 2011 |
| Je Proffservice AS | Transport & logistics | 2008 |
| Jellestadveien 1 Seksjon 1 AS | Real estate | 2022 |
| Jens Dahl AS | Construction | 1991 |
| Jernbanegata 16 AS | Real estate | 1999 |
| Jernbanegata Næringsutvikling AS | Real estate | 2007 |
| JH Bygg AS | Construction | 2012 |
| Jhsinvest AS | | 2023 |
| JL Kommunikasjon AS | Professional & scientific | 2019 |
| JL Toppteknik AB | Wholesale & retail | 2013 |
| JM Gjenvinning AS | Water & waste | 2019 |
| Jo Eiendom AS | Construction | 2007 |
| John Deere Forestry AS | Wholesale & retail | 1990 |
| Jol Drift AS | Health & social care | 2007 |
| Jonas Lies Gate 2 AS | Real estate | 2025 |
| Jonassen Farmasøytiske AS | | 2012 |
| Jonex AS | Real estate | 1992 |
| JSV 10 AS | Real estate | 2008 |
| JTB Invest AS | | 2017 |
| Jørgensen Spesialtransport AS | Transport & logistics | 1994 |
| Ka Maskin AS | Professional & scientific | 2025 |
| Ka Maskin Og Jernbaneservice AS | Manufacturing | 2018 |
| Ka-Ta Da | Information & communication | 2010 |
| Kafé Bohem Baanerudgården AS | Hospitality | 2018 |
| Karl Ragnar Rimfeldt AS | Real estate | 1997 |
| Kasio Holding AS | Real estate | 2016 |
| Kastanjelunden AS | Real estate | 2005 |
| KB Beauty AS | Other services | 2023 |
| KB Gruppen AS | Construction | 2015 |
| KB Gruppen Eiendom AS | Real estate | 2012 |
| KB Gruppen Eiendom Siva AS | Real estate | 2019 |
| KB Gruppen Kongsvinger AS | Manufacturing | 1965 |
| KB Spennteknikk AS | Manufacturing | 1993 |
| KB Øst AS | Professional & scientific | 2014 |
| Kbe Maskinutleie AS | Administrative & support | 2019 |
| KBH Drift AS | Hospitality | 2024 |
| KBK Invest AS | Financial services | 2014 |
| Kda Eiendom AS | Real estate | 2024 |
| Kebab 95 AS | Hospitality | 2015 |
| Keov AS | Financial services | 2015 |
| Kev Holding AS | Financial services | 2013 |
| Kinyko Eiendom AS | Real estate | 2000 |
| Kistmyra Eiendom AS | Real estate | 2017 |
| Kjetil Hjerpset AS | Arts & recreation | 2022 |
| KL Kvalitetsveis AS | Manufacturing | 2018 |
| KL Varme AS | Administrative & support | 2019 |
| Kldiscovery Ontrack AS | Information & communication | 2005 |
| Klinikk for Psykologbehandling AS | Health & social care | 2011 |
| Kobbl Eiendom AS | Real estate | 2013 |
| Kobbl Forretningsbygg AS | Real estate | 2018 |
| Kobbl Utvikling AS | Real estate | 2021 |
| Koleg AS | Health & social care | 1987 |
| Kongsbygg AS | Construction | 2018 |
| Kongsgruppen AS | Transport & logistics | 2026 |
| Kongspow AS | Professional & scientific | 2021 |
| Kongsvinger & Smedtorp Trafikkskole AS | Education | 1997 |
| Kongsvinger Antirust AS | Other services | 2022 |
| Kongsvinger Apotek AS | Wholesale & retail | 2016 |
| Kongsvinger Betong AS | Real estate | 1994 |
| Kongsvinger Betong Eiendom AS | Real estate | 2026 |
| Kongsvinger Bilco Eiendom AS | Real estate | 1958 |
| Kongsvinger Bilhåndvask Da | Other services | 2006 |
| Kongsvinger Bilsenter AS | Wholesale & retail | 2014 |
| Kongsvinger Budget Hotel AS | Hospitality | 2016 |
| Kongsvinger Bygg & Eiendom AS | Real estate | 2015 |
| Kongsvinger Centrallaboratorium AS | Manufacturing | 1979 |
| Kongsvinger Eiendom AS | Real estate | 2019 |
| Kongsvinger Eiendom Holding AS | Real estate | 2018 |
| Kongsvinger Elektriske AS | Wholesale & retail | 1971 |
| Kongsvinger Forretningsbygg AS | Real estate | 1989 |
| Kongsvinger Frukt Og Grønt AS | Wholesale & retail | 2025 |
| Kongsvinger Golfanlegg AS | Real estate | 2011 |
| Kongsvinger Hage & Utemiljø Ans | Administrative & support | 2009 |
| Kongsvinger Hotell Eiendom AS | Hospitality | 2002 |
| Kongsvinger Hudcenter AS | Health & social care | 2016 |
| Kongsvinger Kjøkken AS | Wholesale & retail | 2018 |
| Kongsvinger Kompetanse - Og Næringssenter AS | Real estate | 2006 |
| Kongsvinger Laserklinikk AS | Health & social care | 2021 |
| Kongsvinger Montessoriskole SA | Education | 2017 |
| Kongsvinger Musikksenter AS | Wholesale & retail | 2011 |
| Kongsvinger Optiske AS | Wholesale & retail | 2017 |
| Kongsvinger Rekruttering AS | Administrative & support | 2024 |
| Kongsvinger Science Park AS | Real estate | 2022 |
| Kongsvinger Sentrumshotell AS | Real estate | 2018 |