| Indutrade Oy | Wholesale & retail | 1979 |
| Indy Oy | Wholesale & retail | 1996 |
| Inee oy | Administrative & support | 2023 |
| Inetex palvelut oy | Construction | 2024 |
| Infinigate Finland Oy | Information & communication | 2017 |
| Infinite Concept Oy | Hospitality | 2018 |
| Info House Oy | Professional & scientific | 2010 |
| Info Totem Oy | Information & communication | 2011 |
| Infobit Oy | Professional & scientific | 1989 |
| Infocall Finland Oy | Administrative & support | 1997 |
| Infonor Oy | Information & communication | 1997 |
| Infra Auvinen Oy | Construction | 2020 |
| Infra-Sähkö Oy | Construction | 2019 |
| InfraOne Oy | Construction | 2017 |
| Infradex Oy | Wholesale & retail | 2007 |
| Infrafin Oy | Wholesale & retail | 1998 |
| Infraktor Oy | Information & communication | 2020 |
| Infralion Oy | Professional & scientific | 2022 |
| Infratek Finland Oy | Construction | 2008 |
| Infrateq Group Ab Oy | Information & communication | 2025 |
| Infuel Oy | Wholesale & retail | 2021 |
| Ingenio Design Oy | Professional & scientific | 2025 |
| Ingenjörsfirma Trans-Auto Oy Aktiebolag | Wholesale & retail | 1993 |
| Ingmar Grönvall & Co | Transport & logistics | 1962 |
| Ingvestman Oy | Real estate | 1997 |
| Inission Power Finland Oy | Manufacturing | 1989 |
| Inission Power Oy | Manufacturing | 1973 |
| Inizia Oy | Administrative & support | 2025 |
| Inner Nature Oy | Education | 2023 |
| InnerTown Oy | Administrative & support | 2021 |
| Inno - Vai Oy | Professional & scientific | 1994 |
| InnoGrove Oy | Professional & scientific | 2025 |
| InnoSAP Technologies Oy | Information & communication | 2024 |
| Innobis Oy | Professional & scientific | 1988 |
| Innofis toimistopalvelut Oy | Wholesale & retail | 1995 |
| Innoforma Oy | Health & social care | 2013 |
| Innoholding Oy | Financial services | 2018 |
| Innoprofit Oy | Professional & scientific | 2015 |
| Innopros Oy | Information & communication | 2009 |
| Innoroof Oy | Construction | 2024 |
| Innospirit Oy | Wholesale & retail | 2005 |
| Innotimo Oy | Professional & scientific | 1999 |
| Innovate Invest Oy | Financial services | 2024 |
| Innovate360 European Consultancy Oy | Professional & scientific | 2023 |
| Innovation Tower Oy | Professional & scientific | 2015 |
| Innox Oy | Information & communication | 2006 |
| Inor Transmitter Oy | Wholesale & retail | 2000 |
| Inrego Oy | Wholesale & retail | 2020 |
| Ins.tsto Taito Oy | Construction | 2024 |
| Ins.tsto Tornberg Oy | Professional & scientific | 1992 |
| Inseneeria OY | Construction | 2020 |
| Insinööripalvelu Harju Oy | Real estate | 2018 |
| Insinööritoimisto AK Partners Oy | Professional & scientific | 2022 |
| Insinööritoimisto Ahti Pänttäjä Oy | Professional & scientific | 1977 |
| Insinööritoimisto E-PLAN Oy | Professional & scientific | 2000 |
| Insinööritoimisto Fagertec Oy | Professional & scientific | 1971 |
| Insinööritoimisto Finspector Oy | Professional & scientific | 2012 |
| Insinööritoimisto Harri Jokela Oy | Professional & scientific | 1986 |
| Insinööritoimisto Heikki Möttönen Oy | Professional & scientific | 2005 |
| Insinööritoimisto J. Tanskanen Oy | Professional & scientific | 1992 |
| Insinööritoimisto Jaakko Purje Oy | Professional & scientific | 1986 |
| Insinööritoimisto Jarmo Taisto Oy | Manufacturing | 1995 |
| Insinööritoimisto Jorma Ojamo Oy | Construction | 1989 |
| Insinööritoimisto Jusli Oy | Professional & scientific | 1993 |
| Insinööritoimisto Kedonperä Oy | Real estate | 2025 |
| Insinööritoimisto Kurkela Oy | Construction | 1994 |
| Insinööritoimisto Martti O. Ojala Oy | Professional & scientific | 2008 |
| Insinööritoimisto Matti Pitkälä Oy | Professional & scientific | 1990 |
| Insinööritoimisto Pekkola Oy | Professional & scientific | 2017 |
| Insinööritoimisto Peltomäki Oy | Construction | 1979 |
| Insinööritoimisto Pitkälä Oy | Professional & scientific | 1989 |
| Insinööritoimisto Raimo Hartikainen Oy | Professional & scientific | 1978 |
| Insinööritoimisto Rainer Ahonen Oy | Professional & scientific | 1990 |
| Insinööritoimisto Rakennetutkimus Oy | Professional & scientific | 1967 |
| Insinööritoimisto Solvit Oy | Professional & scientific | 2017 |
| Insinööritoimisto Suunnittelutekniikka Oy | Professional & scientific | 2010 |
| Insinööritoimisto TALVI Oy | Professional & scientific | 2014 |
| Insinööritoimisto Taitosähkö Oy | Construction | 1999 |
| Insinööritoimisto Tecnopoint Oy | Professional & scientific | 1988 |
| Insinööritoimisto Ventac Oy | Professional & scientific | 2002 |
| Insinööritoimisto Vesiniksi Oy | Professional & scientific | 1979 |
| Insinööritoimisto Vojox Oy | Professional & scientific | 2018 |
| Insmac Oy | Construction | 1981 |
| InspectorBros Aerial Oy | Professional & scientific | 2016 |
| Inspon Trading Oy | Wholesale & retail | 2020 |
| Instalco Finland Oy | Construction | 1991 |
| Insulting Consulting Oy | Professional & scientific | 2025 |
| Integra Expert Oy | Professional & scientific | 2025 |
| Integrated E-Solutions Finland Oy | Information & communication | 2000 |
| Integro Rakennus Oy | Construction | 2021 |
| Intelligent Machine RPA Oy | Information & communication | 2020 |
| Intellisolv Oy | Information & communication | 2003 |
| Intema Oy ( Integration & Management) | Real estate | 2017 |
| Inter Omnia Group Oy Ab | Transport & logistics | 2017 |
| InterTechno Training Oy | Information & communication | 2011 |
| Interactiva Solutions Ky | Information & communication | 2003 |
| Interactive Online Technologies Oy | Information & communication | 2021 |
| Interenv Oy | Construction | 2019 |
| Interflon Finland Oy | Wholesale & retail | 2023 |
| Interior Design Helsinki Oy | Professional & scientific | 2021 |