| JN InfraConsulting Oy | Professional & scientific | 2021 |
| JPL Taxiservice Ab Oy | Transport & logistics | 2020 |
| JU Consulting Ab Oy | Professional & scientific | 2025 |
| Jaakon Metalli Oy | Manufacturing | 2015 |
| Jaca Invest Ab | Real estate | 2023 |
| Janatekniikka Oy | Professional & scientific | 1996 |
| Janne & Emil Rakennus Oy | Construction | 2023 |
| Jannes Kräftor Ab Oy | Wholesale & retail | 2018 |
| Jebeco Cleaning Ab Oy | Administrative & support | 2023 |
| Jennica Investment Ab | Other services | 2016 |
| JettZi öppet bolag | Administrative & support | 2021 |
| Josuko Oy | Administrative & support | 1979 |
| Jovli Oy | Financial services | 2020 |
| Joyful Services Oy Ab | Hospitality | 2024 |
| Juniper Hill Ab | Information & communication | 2026 |
| Juridisk byrå Henricson & Kietz Lakiasiaintoimisto | Professional & scientific | 1988 |
| K Concept Ab | Administrative & support | 2022 |
| K. Jousmaa Oy | Construction | 1978 |
| K.J.E. Sjöblom Ab | Professional & scientific | 2009 |
| KAJM Rakennuspalvelu Oy | Construction | 2019 |
| KARU Development Oy | Professional & scientific | 2025 |
| KH Tyres Oy Ab | Wholesale & retail | 2024 |
| KMK - Invest Ab | Financial services | 1986 |
| Kaa-Vex Oy | Administrative & support | 1987 |
| Kalevi Karusuo Oy | Professional & scientific | 1970 |
| Kallnäs Ab Oy | Construction | 2020 |
| Karamar Oy | Real estate | 1993 |
| Kardonar Bioenergy Solutions Oy Ab | Professional & scientific | 2005 |
| Karipo Oy | Information & communication | 2020 |
| Karisbygdens Sjuktransport Kb - Karjaanseudun Sairaankuljetus Ky | Health & social care | 1982 |
| KarmeeKurmee Oy | Hospitality | 2025 |
| Kauppatorin Timanttiporaus Oy | Construction | 1995 |
| Kb Cute And Cuddly | Wholesale & retail | 2010 |
| Kb Ekenäs Bokförings- och Disponenttjänst - Tammisaaren Tili- ja Isännöintipalvelu Ky | Professional & scientific | 1990 |
| Kb El-Fixe Ky | Construction | 1980 |
| Kb Flora & Fauna Ky, Monica Bäckman | Wholesale & retail | 1987 |
| Kb Kurt Österberg Ky | Transport & logistics | 1990 |
| Kb Mäster Grön Ky | Wholesale & retail | 1991 |
| Kb Peneva Ky | Manufacturing | 1988 |
| Kenfix Oy Ab | Administrative & support | 2010 |
| Kennel Zionella's Oy | Agriculture & fishing | 2020 |
| Kenvest Oy | Real estate | 1990 |
| Kesti MotorSports Oy | Other services | 2024 |
| Keyforce Engineering Oy | Wholesale & retail | 2003 |
| Kiinster Oy Ab | Professional & scientific | 2017 |
| Kiinteistö Oy Elisabetslund | Real estate | 1991 |
| Kiinteistö Oy Fjällettan Ab | Real estate | 1992 |
| Kiinteistö Oy Helmiranta | Real estate | 1989 |
| Kiinteistö Oy Tammisaaren Mäntykallio | Real estate | 1994 |
| Kiinteistö Oy Villa Skåldö | Real estate | 2011 |
| Kiinteistöosakeyhtiö C Box | Real estate | 2014 |
| Kiki & Co Oy | Professional & scientific | 2020 |
| Kirpal Oy | Hospitality | 2021 |
| Kollage Oy | Wholesale & retail | 2007 |
| Kommanditbolag Bokföringsbyrå Leif Lindholm Tilitoimisto Kommandiittiyhtiö | Professional & scientific | 1975 |
| Kommanditbolaget Olof Björkqvist | Hospitality | 1984 |
| Koneurakointi Röman Oy | Agriculture & fishing | 2009 |
| Kontoristen Ab Oy | Professional & scientific | 2017 |
| Kotiunelmia Oy | Real estate | 2023 |
| Kouhia Oy | Transport & logistics | 1961 |
| Kraft Research Ab | Professional & scientific | 2022 |
| Krockreparation Jung Ab | Other services | 2021 |
| Kropsu Investment Oy | Administrative & support | 2021 |
| Kråkholmen Invest Ab | Other services | 2012 |
| Kullani Oy | Financial services | 1994 |
| Ky G-Trans Kb | Transport & logistics | 1989 |
| Ky Timotrans Kb | Transport & logistics | 1983 |
| L I Woodlog Ab | Wholesale & retail | 1994 |
| L&G Pajupuhdistamo Oy | Water & waste | 2012 |
| L-O Backman Kb | Professional & scientific | 1984 |
| LB Trading Oy | Other services | 2015 |
| Leds Rock Ky | Wholesale & retail | 2015 |
| LRS Marine OY AB | Manufacturing | 2026 |
| LVI-Tavara Raasepori Oy | Wholesale & retail | 2017 |
| La Max Invest Oy | Real estate | 2024 |
| Ladies Wear Scandinavia Oy Ab | Wholesale & retail | 1995 |
| Lagoa Consulting Oy | Professional & scientific | 2021 |
| Laiska Ebba Oy | Manufacturing | 2021 |
| Laituripalvelu Sipola Oy Ab | Arts & recreation | 2013 |
| Lars-Erik Ekholm Oy | Real estate | 1982 |
| LedLife Oy | Wholesale & retail | 2018 |
| Leksaksaffär Toppen Ab | Wholesale & retail | 2012 |
| Lerocom Oy | Professional & scientific | 1998 |
| Lesprit Oy Ab | Professional & scientific | 1991 |
| Liflender Holdings Ab | Financial services | 2020 |
| Lighthouse Finland Oy | Professional & scientific | 2022 |
| Lilla Skärgårdsbageriet Öppet bolag | Manufacturing | 2010 |
| Limerock Oy Ab | Wholesale & retail | 1995 |
| Lindbom Visions Oy | Information & communication | 2018 |
| Local Growth Ab | Real estate | 2021 |
| Localoca Ab | Administrative & support | 2019 |
| Loppis Småtting Ab | Wholesale & retail | 2023 |
| Luan Oy | Hospitality | 2017 |
| Lunacare Oy Ab | Health & social care | 2011 |
| Lunchpaus Ab | Information & communication | 2008 |
| Lund Boats Finland Oy | Wholesale & retail | 2014 |
| Luontotyö Solja Gehbauer Oy | Administrative & support | 2025 |
| Lydmans Concept AB | Real estate | 2025 |
| M.B-Marketing Ab | Wholesale & retail | 2007 |
| Mad-Solar AB | Wholesale & retail | 2022 |