| Idea Sähkö Oy | Construction | 2025 |
| Iikkoo Invest Oy | Financial services | 2024 |
| Im SiTe Oy | Real estate | 2023 |
| Insinööritoimisto P.A. Tupamäki Oy | Professional & scientific | 1977 |
| Ipe Yhtiö Oy | Construction | 2023 |
| Isopussi Oy | Information & communication | 2024 |
| J Koti Oy | Construction | 2006 |
| J&J Kiintokaluste Oy | Manufacturing | 2021 |
| J&R Service Uusimaa Oy | Construction | 2018 |
| J&S Hannonen | Real estate | 1965 |
| J.Piiroinen Oy | Administrative & support | 2024 |
| JHC Cars Oy | Wholesale & retail | 2021 |
| JL-Kiinteistötaito Oy | Administrative & support | 2008 |
| JM-Air Oy | Construction | 1995 |
| JMS Group Oy | Financial services | 2026 |
| JODERA Consulting Oy | Professional & scientific | 2021 |
| JSP Life Oy | Arts & recreation | 2016 |
| JSR Auto Ky | Wholesale & retail | 1999 |
| JT Diamonds Oy | Construction | 2024 |
| Jakko Oy | Transport & logistics | 2024 |
| Jemival Oy | Construction | 2023 |
| Jetlex Oy | Manufacturing | 1997 |
| Juha Snell Oy | Manufacturing | 1975 |
| Juhani Vasko Oy | Construction | 1991 |
| Jukka Sohlman Oy | Manufacturing | 1979 |
| Junttapojat Oy | Construction | 1993 |
| Jurima Oy | Manufacturing | 1976 |
| Jyrki Karlsson Consulting Oy | Administrative & support | 2020 |
| Järvenpään Tuotetekno Oy | Wholesale & retail | 1992 |
| Järvenpään Yrittäjänkatu 15 Oy | Real estate | 2010 |
| Järvinen Rakennuspalvelu Oy | Construction | 2026 |
| K & A Partners Oy | Professional & scientific | 2020 |
| Ka-Kuljetus OY | Transport & logistics | 2023 |
| KK-Kiito Oy | Transport & logistics | 2008 |
| KM Palvelut Oy | Health & social care | 2022 |
| KPJ Kiinteistöt Oy | Real estate | 2020 |
| KSM Gruppi OY | Construction | 2021 |
| KT Prosessipesu Oy | Financial services | 2013 |
| Kaimoner Oy | Construction | 1984 |
| Kar-Vi-Pelti Oy | Manufacturing | 1990 |
| KarlStream Oy | Construction | 2023 |
| Kastanja Finland Oy | Arts & recreation | 2014 |
| Kattohuolto Kaipainen Oy | Construction | 2025 |
| KatvaSoft Oy | Information & communication | 2013 |
| Kellis Productions Oy | Information & communication | 2023 |
| Kello & Kellari Oy | Hospitality | 2026 |
| Kellokosken Asennus ja Sähkö Oy | Construction | 2016 |
| Kellokosken Jäähalli Oy | Arts & recreation | 1999 |
| Kellokosken Koneistus Oy | Manufacturing | 1996 |
| Kellokosken Reeni ja Rentoutus Oy | Arts & recreation | 2023 |
| Kellokosken Woimalaitos oy | Other services | 2021 |
| Keski-Uudenmaan Tili avoin yhtiö | Professional & scientific | 2009 |
| Keski-Uudenmaan hitsauspalvelu oy | Manufacturing | 2016 |
| Ketola Bros Oy | Professional & scientific | 2013 |
| Kiint. Oy Rajalinna | Real estate | 1997 |
| Kiinteistö Oy Järvenpään Hirvitie 3 | Real estate | 1991 |
| Kiinteistö Oy Pyhtään Mäntyniemi | Real estate | 1993 |
| Kiinteistö Oy Salmilamminkaita 3 | Hospitality | 2022 |
| Kiinteistö Oy Tuuli | Real estate | 1998 |
| Kiinteistö Oy Tuusulan Väinö-Kaarina | Real estate | 1997 |
| Kiinteistökunto Oy | Real estate | 2009 |
| Kilakka Oy | Real estate | 2008 |
| Kimmoisin Oy | Professional & scientific | 2024 |
| Kirjanpito Mäntymäki Oy | Professional & scientific | 1982 |
| Kivi Liekari Oy | Construction | 2014 |
| Kiviasennus ja -saneeraus Koponen Oy | Administrative & support | 1977 |
| Kivimäki Horses Oy | Health & social care | 2012 |
| Kivivasara Logistiikkapalvelut Oy | Transport & logistics | 2009 |
| Konepalvelu Sohlman Oy | Administrative & support | 2001 |
| Koskikello Oy, Vesa Lamppu | Wholesale & retail | 1989 |
| Kuljetus Keskitalo Ky | Transport & logistics | 2002 |
| Kuljetusliike Martti Valo kommandiittiyhtiö | Transport & logistics | 1983 |
| Kuljetuspalvelu Jamia Oy | Transport & logistics | 2016 |
| Kuljetuspalvelu Konsta Riikonen oy | Transport & logistics | 2012 |
| Kumpuco Oy | Financial services | 2021 |
| Kylmäkuljetus Aalto Oy | Administrative & support | 2022 |
| Kärki Group Oy | Administrative & support | 2025 |
| Kärkisähkö Oy | Construction | 2020 |
| Kärkitekniikka Oy | Construction | 2023 |
| LKS-Invest Oy | Wholesale & retail | 1991 |
| Lasimestari 110 Oy | Real estate | 2024 |
| Lastensuojelupalvelut Nummenlinna Oy | Health & social care | 2011 |
| Lastensuojelupalvelut Villa Sanka Oy | Health & social care | 2018 |
| Lifestyle Atelier Oy | Wholesale & retail | 2020 |
| Live Sound Finland Oy | Arts & recreation | 2016 |
| Livia Medical Oy | Wholesale & retail | 2014 |
| Lomaratti Oy | Administrative & support | 2025 |
| Lostballs Oy | Professional & scientific | 2023 |
| Lounaan Negomex Oy | Construction | 2020 |
| Luikku Co Oy | Wholesale & retail | 2011 |
| Luna Innovation Oy | Information & communication | 2021 |
| LuxSus Oy | Other services | 2017 |
| Lähettipalvelu Fast Oy | Transport & logistics | 2019 |
| Lämpöyö OY | Hospitality | 2026 |
| MAC Autohuolto Oy | Other services | 2025 |
| MHL Rakennus Oy | Construction | 2023 |
| MJ Cabs Oy | Transport & logistics | 2019 |
| MKH Infra Oy | Construction | 2023 |
| Mmj-Rakennus OY | Construction | 2018 |
| MSG-Kiinteistöt Ky | Real estate | 1982 |