| Jeppfix Ab | Construction | 2021 |
| Jeppis Fried Chicken Oy | Hospitality | 2023 |
| Jeppis Garage Ab Oy | Real estate | 2020 |
| Jeppis Gym avoin yhtiö | Arts & recreation | 1995 |
| Jeppis Moposhop Ab | Wholesale & retail | 2022 |
| Jeppis Padel Ab | Arts & recreation | 2025 |
| Jesella Ab | Education | 2026 |
| Jesse Haavisto Oy | Construction | 2024 |
| Jifix Ab Oy | Other services | 2018 |
| JohaDes OY | Construction | 2023 |
| JonSMedia Ab | Wholesale & retail | 2019 |
| Jonttis EL och Service AB | Construction | 2021 |
| Jorilco Oy | Professional & scientific | 1993 |
| Joupers VVS - LVI Ab Oy | Construction | 2013 |
| Jungell Consulting Ab | Professional & scientific | 1993 |
| Junto Investment Ab | Real estate | 2017 |
| Jupiter4movie öppet bolag | Information & communication | 2014 |
| Juristbyrå Annika Holmström Ab | Professional & scientific | 1991 |
| JÄST Pizza Oy | Hospitality | 2026 |
| Jästhuset öppet bolag | Real estate | 2016 |
| K & J Holding Oy Ab | Financial services | 2021 |
| K & K Meatservice Oy Ab | Manufacturing | 2009 |
| K-Music Öppet Bolag | Wholesale & retail | 2012 |
| K. Andersson Kb | Wholesale & retail | 1999 |
| K.-E. Enlund OY AB | Real estate | 1986 |
| KA Forresters Ab | Agriculture & fishing | 2015 |
| KAMB målarservice Ab | Construction | 2025 |
| Kamship OY | Manufacturing | 2023 |
| KENTS Måleritjänst - Maalauspalvelu Ab Oy | Construction | 2017 |
| KG Invest Oy | Administrative & support | 2019 |
| KH Kaffia Ab | Hospitality | 2016 |
| KIM-Tuote Ab Oy | Manufacturing | 2012 |
| KORW Oy Ab | Hospitality | 2023 |
| KS Mäenpää AB | Professional & scientific | 2013 |
| KS-Project Ab | Professional & scientific | 2019 |
| KSST-Invest Oy | Real estate | 2025 |
| KVO Invest Ab | Financial services | 2025 |
| Kachow Capital AB | Financial services | 2025 |
| Kahvitella Oy | Hospitality | 2023 |
| Kaj Häggblom Ab | Construction | 1998 |
| Kali ravintola oy | Hospitality | 2026 |
| Kallan Invest Ab | Financial services | 2023 |
| Kallman Ab | Professional & scientific | 2015 |
| Kamphouse Ky | Construction | 2004 |
| Katternö Kraft Oy Ab | Energy | 1957 |
| Katternö Kärnkraft Oy Ab | Energy | 2007 |
| Kauneushoitola Calla Oy | Other services | 2020 |
| Kb A. Käld & Co Ky | Wholesale & retail | 1987 |
| Kb Alholmens Slip - Leppäluodon Telakka Ky | Manufacturing | 1980 |
| Kb Bokföringsbyrå Henrik Åkerlund Tilitoimisto Ky | Professional & scientific | 1983 |
| Kb Bröderna Björk Veljekset Ky | Manufacturing | 1982 |
| Kb Denix Ky | Wholesale & retail | 1990 |
| Kb Fasad 29 Ky | Manufacturing | 1984 |
| Kb KH-Carservice Ky | Wholesale & retail | 1987 |
| Kb Re-Car Ky | | 1990 |
| Kb S Sandlin Ky | Wholesale & retail | 1975 |
| Kb Super-Team Ky | Other services | 1983 |
| Kb T. Jansson Ky | Manufacturing | 1991 |
| Kb Tupeli Ky | Hospitality | 1985 |
| Kb Vörå Betongtransport | Manufacturing | 1984 |
| Kenths Åkeri AB | Transport & logistics | 2009 |
| Kents Fix Ab | Wholesale & retail | 2022 |
| Kenweld Ab | Manufacturing | 1998 |
| Kiinteistö Oy Choraeuksenkatu 11, Pietarsaari | Real estate | 2000 |
| Kiinteistö Oy Hällan | Real estate | 1994 |
| Kiinteistö Oy Jaakonhalli | Real estate | 1972 |
| Kiinteistö Oy Jakopuu | Real estate | 2016 |
| Kiinteistö Oy Kangastie 16 | Real estate | 2001 |
| Kiinteistö Oy Permonkaarre 109 | Real estate | 2007 |
| Kiinteistö Oy Pietarsaaren Pohjanlahdenkatu 61 | Real estate | 2004 |
| Kiinteistö Oy Pietarsaaren Tehtaankatu 13 | Real estate | 2001 |
| Kiinteistö Oy Pietarsaaren Victoria | Real estate | 2005 |
| Kiinteistö Oy Ristisuonraitti | Real estate | 2000 |
| Kiinteistö Oy Santa-Ylläs | Real estate | 1986 |
| Kiinteistö Oy Skutnäsinkatu 64 | Real estate | 2010 |
| Kiinteistö Oy Taljasepänkatu 14 | Real estate | 1995 |
| Kiinteistö Oy Teollisuustie 22 | Real estate | 2013 |
| Kiinteistö Oy Tosikkomaja | Real estate | 1990 |
| Kiinteistö Oy WestNorth9 | Real estate | 2019 |
| Kiinteistöosakeyhtiö Kitisen Kihhaus | Real estate | 1992 |
| Kiinteistöosakeyhtiö Starabyntie | Real estate | 1994 |
| Kim Södergård Ab | Agriculture & fishing | 1996 |
| Kim-Olofs Ab | Manufacturing | 2019 |
| KimSult Ab | Professional & scientific | 2015 |
| Kiosk 7 öppet bolag | Hospitality | 2019 |
| Kirria Oy | Professional & scientific | 2019 |
| Kisor Mink ab | Agriculture & fishing | 2012 |
| KisorBo ab | Financial services | 2021 |
| Kivikangas Oy | Wholesale & retail | 1981 |
| Klaara Partners Oy | Professional & scientific | 2025 |
| Kobox Invest Oy | Construction | 2023 |
| Kokin Paras Oy Ab | Manufacturing | 2021 |
| Komag Ab | Real estate | 2021 |
| Kommandiittiyhtiö Meccon Kommanditbolag | Professional & scientific | 1986 |
| Kommanditbolag R. Westerlund Kommandiittiyhtiö | Wholesale & retail | 1978 |
| Kompost Audio Ab | Information & communication | 2025 |
| Koncentra Pistons Oy | Manufacturing | 2016 |
| Koodaten Enterprises Oy | Information & communication | 2018 |
| Kronholm & Co | Agriculture & fishing | 1975 |
| Kuhlberg Invest Ab Oy | Real estate | 2015 |