| KoKo-huolto Ky | Other services | 2016 |
| Kobby Oy | Financial services | 2021 |
| Kodikas Tähti-Koti Oy | Construction | 2015 |
| Kodikkain Oy | Real estate | 2021 |
| Kohtaava Oy | Health & social care | 2022 |
| Kohtilapio Oy | Wholesale & retail | 2007 |
| Koitajo Oy | Health & social care | 2026 |
| Koiviston Auto Group Oy | Professional & scientific | 2021 |
| Koiviston Auto Lahti Oy | Transport & logistics | 2004 |
| Koivulan Leipomo Oy | Manufacturing | 1995 |
| Kojoma Oy | Wholesale & retail | 2023 |
| Koki Finland Oy | Wholesale & retail | 2004 |
| Kokontti Oy | Administrative & support | 2018 |
| Kolamek Oy | Real estate | 1994 |
| Kolcar Ky | Other services | 1992 |
| Koli Service Oy | Administrative & support | 2007 |
| Kolli Invest Oy | Financial services | 1990 |
| Komee Consulting Oy | Information & communication | 2016 |
| Kommandiittiyhtiö Veljekset Backman Bröderna Kommanditbolag | Manufacturing | 1954 |
| Komplexi avoin yhtiö | Professional & scientific | 2017 |
| KoneKorja Oy | Administrative & support | 2024 |
| Konehuolto P. Mäkinen Ky | Manufacturing | 1978 |
| Koneistustyökalut Patrikainen Oy | Wholesale & retail | 1997 |
| Konekorjaus ja Maalaus Laukkanen Ky | Other services | 2004 |
| Konepesonen Ky | | 1986 |
| Koneruutu Alvar Harju ja Kump. | Wholesale & retail | 1976 |
| Koneurakointi A.Luuri Oy | Construction | 2024 |
| Koneurakointi Ari Aro Oy | Construction | 1996 |
| Koneurakointi Koljonen Oy | Construction | 2007 |
| Konsultointi E & N Oy | Real estate | 1984 |
| Konsultointi Salomaa Oy | Professional & scientific | 2000 |
| Konsulttikeskus Oy | Professional & scientific | 1971 |
| KontaktiVerkko Suomi Oy | Professional & scientific | 2008 |
| Konttoritaito Oy | Wholesale & retail | 1991 |
| Konttoritarvike Promesa Oy | Wholesale & retail | 1998 |
| Koonta Solutions Oy | Information & communication | 2026 |
| Koppelonperän kalatorppa Avoin yhtiö | Professional & scientific | 2004 |
| Korona Kapital Oy | Real estate | 2020 |
| Korpi Design Oy | Manufacturing | 2009 |
| Korppi Group Oy | Professional & scientific | 2025 |
| Korttiopisto Oy | Education | 2022 |
| Korxon Oy | Wholesale & retail | 2020 |
| Kos-Ni Oy | Wholesale & retail | 1993 |
| KosKri Oy | Professional & scientific | 2023 |
| Koskelo Bus Oy | Transport & logistics | 1977 |
| Koski Asunnot Oy | Real estate | 2021 |
| Koski Meka Oy | Manufacturing | 2026 |
| Kosofinn Oy | Manufacturing | 1974 |
| Kotihoito Hilma Oy | Health & social care | 2022 |
| Kotimestarit Oy | Construction | 1988 |
| Kotineutroni Oy | Real estate | 2024 |
| Kotipalvelu Toivo Oy | Health & social care | 2022 |
| Kotipalvelu Tupastuttu Oy | Administrative & support | 2004 |
| Kotkan Tähti Oy | Construction | 2015 |
| Kotkanniemen Saneeraus Ky | Administrative & support | 2013 |
| Kotkaway Oy | Information & communication | 2025 |
| Koulutekniikka jiiri Ky | Wholesale & retail | 1985 |
| Koulutustalo Oppia Ky | Education | 2012 |
| Kovapro events Oy | Arts & recreation | 2017 |
| Kovasemi OY | Construction | 2026 |
| Koze Oy | Construction | 2015 |
| Kraidie Consulting Oy | Information & communication | 2023 |
| Kraken works Oy | Construction | 2019 |
| Krantec Oy | Construction | 2006 |
| Kreation Kapital Oy | Professional & scientific | 2022 |
| Kreman Capital Oy | Financial services | 2021 |
| Kriisi- ja arviointipalvelu Kompassi Oy | Health & social care | 2018 |
| Kristian Events Oy | Arts & recreation | 2023 |
| Kroko Print Solutions Oy | Information & communication | 2004 |
| Kroxa Group Oy | Professional & scientific | 2025 |
| Krual OY | Real estate | 2022 |
| Kruunu Keittiöt Oy | Wholesale & retail | 2026 |
| Ks Studio Oy | Other services | 2020 |
| Kuitu Ässä OY | Construction | 2025 |
| Kuitusen Keikka Ky | Transport & logistics | 2018 |
| Kukanoksa Oy | Real estate | 1985 |
| Kukaon Oy | Administrative & support | 2021 |
| KukkaKaristo Oy | Wholesale & retail | 2016 |
| Kukkapiilo Oy | Wholesale & retail | 2024 |
| Kukkatarha Koskinen Oy | Wholesale & retail | 1993 |
| Kukkeli Oy | Professional & scientific | 2025 |
| Kukkulan Lämpöpumppu Oy | Wholesale & retail | 2022 |
| Kukonkoski Oy | Real estate | 2006 |
| Kuljetus A. Rantanen Oy | Transport & logistics | 2015 |
| Kuljetus J Taipanen Oy | Transport & logistics | 2001 |
| Kuljetus J. Heinonen Oy | Transport & logistics | 2006 |
| Kuljetus Jere Laine Ky | Transport & logistics | 2016 |
| Kuljetus Jooseppi Oy | Transport & logistics | 2023 |
| Kuljetus Kalenius Ky | Transport & logistics | 2008 |
| Kuljetus Kivistö Ky | Transport & logistics | 1996 |
| Kuljetus Lakkapää Oy | Transport & logistics | 2012 |
| Kuljetus M. Juuti Ky | Transport & logistics | 2013 |
| Kuljetus M. Levänen Ky | Transport & logistics | 1996 |
| Kuljetus M. Pykälä Oy | Transport & logistics | 2026 |
| Kuljetus Markku Lemmetty Oy | Transport & logistics | 2009 |
| Kuljetus O. Toivonen Oy | Transport & logistics | 2007 |
| Kuljetus O.J. Nieminen Oy | Transport & logistics | 1996 |
| Kuljetus Oy Kauko Helenius | Transport & logistics | 1977 |
| Kuljetus Petri Salminen Oy | Transport & logistics | 2007 |
| Kuljetus R. Niittynen Oy | Transport & logistics | 1991 |