| Lifjell Vinterland AS | Arts & recreation | 1998 |
| Lifjellstua AS | Hospitality | 2002 |
| Lifjellstua Eiendom AS | Hospitality | 2002 |
| LKF Holding AS | | 2024 |
| LKV Invest AS | Real estate | 2015 |
| Lokalmat Telemark Holding AS | Professional & scientific | 2025 |
| Lootlab AS | Wholesale & retail | 2023 |
| Lowkey Management Da | Professional & scientific | 2020 |
| Lykkeberg Boligfelt Bø AS | Real estate | 2021 |
| Lønnestad Invest AS | | 2019 |
| M Sønstebø AS | Real estate | 1967 |
| M. Sønstebø Holding AS | Wholesale & retail | 2005 |
| Mafela AS | Real estate | 2015 |
| Marcel Wetemans Beheer B.V. Nuf | Real estate | 2026 |
| Maurtuva Barnehage SA | Education | 1995 |
| Maxima Helse AS | Health & social care | 2013 |
| MB 00 Invest AS | | 2025 |
| MH Utvikling AS | Real estate | 2007 |
| Michael Scott Holding Company AS | | 2022 |
| Midt Telemark Auto AS | Wholesale & retail | 2021 |
| Midt Telemark Invest AS | Information & communication | 1985 |
| Midt-Telemark Bilservice AS | Other services | 2024 |
| Midt-Telemark Brannservice AS | Wholesale & retail | 1997 |
| Midt-Telemark Breiband AS | Information & communication | 2000 |
| Midt-Telemark Bygg AS | Construction | 2003 |
| Midt-Telemark Flis Og Mur AS | Construction | 2019 |
| Midt-Telemark Graveservice AS | Construction | 2020 |
| Midt-Telemark Jordforedling AS | Water & waste | 2021 |
| Midt-Telemark Kommunale Eigedom AS | Real estate | 1991 |
| Midt-Telemark Næringspark AS | Real estate | 2009 |
| Midt-Telemark Og Nome Utvikling AS | Professional & scientific | 2003 |
| Midt-Telemark Pizza AS | Hospitality | 2009 |
| Midt-Telemark Pumpeservice AS | Construction | 2012 |
| Midt-Telemark Regnskap AS | Professional & scientific | 2005 |
| Midt-Telemark Stisykling AS | Arts & recreation | 2022 |
| Midt-Telemark Synssenter AS | Wholesale & retail | 2004 |
| Midt-Telemark Vedproduksjon AS | Wholesale & retail | 2018 |
| Mikkel Handel AS | Wholesale & retail | 2015 |
| Milekåsa Holding AS | | 2019 |
| Mindalen Steinanlegg AS | Construction | 2019 |
| Minde Håndverktjenester AS | Construction | 2017 |
| MKV Invest AS | Real estate | 2016 |
| Mobile Bø AS | Wholesale & retail | 1988 |
| Moksa AS | Education | 2018 |
| Mom Entreprenør Da | Agriculture & fishing | 2006 |
| Montering AS | Construction | 2021 |
| MRT Eigedom AS | Real estate | 2017 |
| MSG Cleaning Systems AS | Wholesale & retail | 2020 |
| MSG Group AS | Real estate | 2022 |
| MSG Holding AS | Professional & scientific | 2017 |
| MT Aktivitetsanlegg AS | Real estate | 2023 |
| MTS Anleggsutvikling AS | Arts & recreation | 2026 |
| Multilux Eigedom AS | Real estate | 2016 |
| Murmester Einar Espedalen AS | Construction | 1999 |
| MVB 09 Invest AS | | 2025 |
| Myhra Maskinverksted AS | Manufacturing | 2012 |
| Mæland Autosenter AS | Wholesale & retail | 1988 |
| Mæland Eigedom AS | Real estate | 1986 |
| Mæland Holding AS | Real estate | 2005 |
| Møbelhuset Bø AS | Wholesale & retail | 1998 |
| Nedre Nes AS | Agriculture & fishing | 2018 |
| Neptun Mur Og Puss Ans | Construction | 1990 |
| New Contour AS | Professional & scientific | 2016 |
| New Future Engineering Services AS | Professional & scientific | 2020 |
| Niras AS | Manufacturing | 1985 |
| Niras Holding AS | Manufacturing | 2005 |
| Nogalo Transport AS | Transport & logistics | 2014 |
| Nordbøhagen AS | Real estate | 2020 |
| Nordbøåsen Utbyggingsselskap AS | Real estate | 2011 |
| Nordic Auto Equipment AS | Wholesale & retail | 2026 |
| Nordic Composites AS | Construction | 2023 |
| Nordic Hosting AS | Information & communication | 2006 |
| Norsjø Eiendom Og Utvikling AS | Real estate | 2017 |
| Norsjø Kammermusikkfest AS | Arts & recreation | 2015 |
| Norsk Hardingfelesenter AS | Arts & recreation | 2010 |
| Norsk Holdings AS | Manufacturing | 2022 |
| Norsk Standard Entreprenør AS | Real estate | 2021 |
| Næs Tele & Data AS | Wholesale & retail | 2011 |
| Oah Invest AS | Real estate | 2008 |
| Obscura AS | Wholesale & retail | 2017 |
| Oddbjørn Braaten AS | Construction | 2006 |
| Olas Eiendom AS | Real estate | 2006 |
| Olav Kasland AS | Professional & scientific | 2022 |
| Olsen Industri Og Overflate Service AS | Manufacturing | 2021 |
| Omb 03 Invest AS | | 2025 |
| Operation AS | | 2007 |
| Oppheimjordet AS | Construction | 2014 |
| Oppheimjordet Utvikling AS | Real estate | 2017 |
| OSU08 AS | | 2021 |
| Optiker Torstein Nyhus A/S | Wholesale & retail | 1988 |
| Pallesen Eiendom AS | Real estate | 1999 |
| Pe-Invest AS | | 2023 |
| Pit-Stop AS | Other services | 2024 |
| Pizza Fjoset AS | Hospitality | 1994 |
| PP Rør AS | Construction | 2014 |
| Proshop AS | Wholesale & retail | 1996 |
| Provence Restaurant AS | Hospitality | 2020 |
| Pust Og Stemme AS | Health & social care | 2023 |
| Reime Biotek AS | Professional & scientific | 2002 |
| Richard Manuel AS | Financial services | 2005 |