| Ihan Hyvä Juontaja Oy | Professional & scientific | 2026 |
| Ihana Academy Oy | Education | 2023 |
| Iiro Hänninen Oy | Health & social care | 2025 |
| Iisalon Rakennuskivi Oy | Wholesale & retail | 1993 |
| Ikigai Pickleball oy | Wholesale & retail | 2024 |
| Ikkunakumppanit Oy | Wholesale & retail | 2018 |
| Ikkunaprinssit avoin yhtiö | Administrative & support | 2014 |
| Ikoni Ikkuna Oy | Wholesale & retail | 2018 |
| Ilimavoimat Oy | Construction | 2023 |
| Ilkanoma Oy | Financial services | 2024 |
| Ilkka Kukkonen Ky | Education | 2017 |
| Ilko Holdings Oy | Financial services | 2024 |
| Ilmainen Neuvo Oy | Real estate | 1998 |
| Ilmapörssi Oy | Construction | 1989 |
| Ilmasiili Oy | Construction | 2006 |
| Ilmastointipalvelu Koponen Ky | Administrative & support | 2010 |
| Ilmastointipalvelu Piipputiimi Oy | Manufacturing | 2002 |
| Ilo Kasvaa Savossa Oy | Arts & recreation | 2020 |
| Imituattori Oy | Arts & recreation | 2018 |
| In Sappco Oy | Construction | 2022 |
| InSoHo Oy | Information & communication | 2022 |
| Incedo Oy | Professional & scientific | 2003 |
| Incight Medical Technologies Oy | Manufacturing | 2025 |
| Info-X Oy | Professional & scientific | 2022 |
| Infra Partners Oy | Professional & scientific | 2003 |
| Ingka Centres Finland Oy | Professional & scientific | 2017 |
| Ingka Centres Kuopio Oy | Real estate | 2007 |
| Inkkari Kioski avoin yhtiö | Wholesale & retail | 1980 |
| Innilän Erä ja Kala Oy | Agriculture & fishing | 2022 |
| InnoVaatio Advisory Oy | Professional & scientific | 2026 |
| Innocomp Ky | Manufacturing | 1992 |
| Innofloor Oy | Wholesale & retail | 2015 |
| Innokem Oy | Manufacturing | 2015 |
| Innolact Agro Oy | Wholesale & retail | 2021 |
| Innolact Ferme Oy | Wholesale & retail | 2021 |
| Innolact Group Oy | Professional & scientific | 2006 |
| Innon Oy | Professional & scientific | 2016 |
| Innosystem Oy | Professional & scientific | 1985 |
| Innote valmennus Oy | Professional & scientific | 1995 |
| Innova Invest Oy | Real estate | 2024 |
| Insaco Group Oy | Construction | 2008 |
| Insinööritoimisto AL-Plan Oy | Professional & scientific | 1997 |
| Insinööritoimisto Aki Kutvonen Ky | Professional & scientific | 2002 |
| Insinööritoimisto Ariconn Oy | Professional & scientific | 2009 |
| Insinööritoimisto Kovarak Oy | Professional & scientific | 2017 |
| Insinööritoimisto Laaturakenne Oy | Professional & scientific | 2005 |
| Insinööritoimisto Murte Oy | Professional & scientific | 2022 |
| Insinööritoimisto Plan & Control Oy | Construction | 2021 |
| Insinööritoimisto Rakenneankkuri Oy | Professional & scientific | 2026 |
| Insinööritoimisto Rakennepiste Oy | Professional & scientific | 1993 |
| Insinööritoimisto SRT Oy | Professional & scientific | 2021 |
| Insinööritoimisto Savon Kunto & Kosteus Oy | Professional & scientific | 2011 |
| Insinööritoimisto Taavitsainen Oy | Construction | 2026 |
| Inskriptio Oy | Information & communication | 2024 |
| Insomniac Oy | Information & communication | 2004 |
| InspecTeam Oy | Real estate | 2012 |
| Instele Oy | Wholesale & retail | 1993 |
| Intako Oy | Construction | 2026 |
| Inter-Viihde Oy | Professional & scientific | 2014 |
| InterLingvo OY | Education | 2020 |
| Interior SmArt Deco Oy | Professional & scientific | 2019 |
| International Transport Heimonen oy | Administrative & support | 2024 |
| Invent Ky | Professional & scientific | 1990 |
| Invers Oy | Professional & scientific | 2020 |
| InvesStar Oy | Financial services | 2005 |
| Invest AiQ Oy | Financial services | 2024 |
| Invest Saarelainen Oy | Real estate | 1988 |
| Investalign Oy | Health & social care | 2022 |
| Investija Oy | Real estate | 2024 |
| Invilog Research Oy | Professional & scientific | 2010 |
| Iocon Oy | Professional & scientific | 2009 |
| Irma Kokkaa Oy | Hospitality | 2024 |
| IroFit Technologies Oy | Information & communication | 2014 |
| Iron Bank Oy | Financial services | 2021 |
| Ironhorse Oy | Wholesale & retail | 2013 |
| Isarvo Koti Oy | Real estate | 2020 |
| Isarvo Tekniikka Oy | Professional & scientific | 1993 |
| Isecon Oy | Construction | 2025 |
| IslabVerkko Oy | Health & social care | 2018 |
| Iso-Kallan Panimo Oy | Manufacturing | 2013 |
| Isompi Visio Oy | Administrative & support | 2020 |
| Istekki Oy | Information & communication | 2009 |
| Isännöinti Koto-Savo Ky | Real estate | 2012 |
| Isännöintipalvelu Isarvo Oy | Real estate | 1996 |
| Isännöintipalvelu Isarvo Oy Tampere | Real estate | 1987 |
| Isännöintisatama oy | Real estate | 2014 |
| Isännöintitienoo Oy | Real estate | 2024 |
| Isännöitsijätoimisto Keijonen Ky ISA | Real estate | 1967 |
| Isäntä Investments Oy | Professional & scientific | 2021 |
| Itech-Bros Oy | Information & communication | 2017 |
| Itkonranta Oy | Real estate | 2024 |
| Itä-Suomen Edunvalvonta Oy | Professional & scientific | 2020 |
| Itä-Suomen Ensiapukoulutus Oy | Education | 2009 |
| Itä-Suomen Hissikonsultointi OY | Professional & scientific | 2025 |
| Itä-Suomen Kuljetus ja Kunnossapito Oy | Transport & logistics | 2014 |
| Itä-Suomen LVI-Palvelu Oy | Construction | 2013 |
| Itä-Suomen Nosturitarkastus Oy | Manufacturing | 2017 |
| Itä-Suomen Rakennuspalvelu Oy | Construction | 2022 |
| Itä-Suomen Taso-Markkinointi Puhdasmatto Avoin yhtiö | Other services | 1992 |
| Itä-Suomen Turvapiste Oy | Administrative & support | 1996 |