| Impossible Mental Health Limited | Health & social care | 2020 |
| Imprint Wonders Limited | Wholesale & retail | 2023 |
| Impro Printing Ltd | Manufacturing | 2014 |
| Improved Health Ltd | Wholesale & retail | 2022 |
| Improved Wholesale Ltd | Wholesale & retail | 2024 |
| Improvised Print Limited | Manufacturing | 2022 |
| IN Car Safety Centre Ltd | Wholesale & retail | 2024 |
| IN Cleaning Services Ltd | Administrative & support | 2025 |
| IN One Piece Removals Ltd | Transport & logistics | 2021 |
| IN Real Life Studio Ltd | Professional & scientific | 2026 |
| IN This Together | Other services | 2021 |
| In-Ovo Fertility Clinics Ltd | Health & social care | 2013 |
| IN2 Design Engineering Holdings Limited | Financial services | 2022 |
| IN2 Design Engineering Limited | Professional & scientific | 2008 |
| Inaltus Limited | Professional & scientific | 2011 |
| Inavate Belfast Ltd | Wholesale & retail | 2023 |
| Inbev Ireland Limited | Financial services | 1964 |
| Inbound Things Limited | Professional & scientific | 2016 |
| Inbox Traders Ltd | Wholesale & retail | 2026 |
| Inca Wasi Ltd | Households | 2025 |
| Incartus Ltd | Financial services | 2011 |
| Inception Studio Limited | Arts & recreation | 2019 |
| Inch 19 Limited | Extraterritorial | 2019 |
| Inch Rock Enterprises Limited | Extraterritorial | 2016 |
| Inch Rock Management Ltd | Real estate | 2016 |
| Inchbervis Limited | Real estate | 2011 |
| Incisiv Ltd | Information & communication | 2018 |
| Incite Hunter Ltd | Wholesale & retail | 2024 |
| Include Youth | Health & social care | 2000 |
| Inclusive Law Ltd | Professional & scientific | 2023 |
| Inclutech Ltd | Information & communication | 2016 |
| Incognito Ltd | Information & communication | 2023 |
| Incorporate Benefits LLP | | 2017 |
| Incorporate Employee Benefits Limited | Financial services | 2003 |
| Incorporate Group Ltd | Financial services | 2024 |
| Incorporate Insurance Services Limited | Financial services | 1994 |
| Incorporate Properties Limited | Real estate | 2023 |
| Incus Interpreting Ltd | Other services | 2019 |
| Independence 4 YOU Ltd | Health & social care | 2018 |
| Independence Day Trading Ltd | Real estate | 2021 |
| Independent Health and Care Providers (NI) | Other services | 1998 |
| Independent Newspapers PLC | | 1924 |
| Independent Plant Hire and Contracts Ltd | Construction | 2005 |
| Indevair Ltd | Construction | 2016 |
| Index Perfect Limited | Information & communication | 2012 |
| India Street Tattoo Limited | Other services | 2016 |
| Indian Ocean Bangor Ltd | Hospitality | 2012 |
| Indico Ltd | Education | 2023 |
| Indie Movie Company Limited | Information & communication | 2009 |
| Indie Saas Ltd | Information & communication | 2021 |
| Indigenous Sea Limited | Wholesale & retail | 1999 |
| Indikus Solutions Ltd | Financial services | 2024 |
| Indu Regs Ltd | Professional & scientific | 2026 |
| Indus Radiology Limited | Health & social care | 2017 |
| Indus Valley Coleraine Ltd | Hospitality | 2018 |
| Industrial Floorcare Machines Ltd | Manufacturing | 2011 |
| Industrial Process Systems Limited | Administrative & support | 2002 |
| Industrial Temps (IT) LLP | | 2015 |
| Industrial Temps Limited | Administrative & support | 1995 |
| Industry Productions Ltd | Arts & recreation | 2019 |
| Industry Properties Ltd | Real estate | 2024 |
| Ineqe Group Limited | Administrative & support | 2011 |
| Inexile Limited | Information & communication | 2020 |
| Infection Prevention Technologies Ltd | Wholesale & retail | 2026 |
| Inferno Infrared Sauna & Sunbed Studios Ltd | Other services | 2020 |
| Infinet Media Ltd | Administrative & support | 2022 |
| Infinite Management Services Ltd | Professional & scientific | 2023 |
| Infinite People Solutions Ltd | Education | 2006 |
| Infinite Success Research Solution Ltd | Professional & scientific | 2023 |
| Infinity Crisis Management Ltd | Education | 2026 |
| Infinity Health Fitness & Coaching Ltd | Arts & recreation | 2022 |
| Infinity Mediaco Ltd | Wholesale & retail | 2014 |
| Infinity Space Ltd | Arts & recreation | 2026 |
| Infinity Sunbeds Ltd | Other services | 2025 |
| Infiniwave Technologies Ltd | Professional & scientific | 2024 |
| Inflyte Limited | Information & communication | 2014 |
| Inform Communications NI Limited | Professional & scientific | 2003 |
| Informing Choices NI (Trading AS Icni) Ltd | Health & social care | 2019 |
| Infosoft NI Ltd | Information & communication | 2007 |
| Infrastructure Analytics Limited | Mining & quarrying | 2016 |
| Ingleford Properties Limited | Real estate | 2002 |
| Ingleside Management Company (NI) Limited | Real estate | 2006 |
| Ingram Cleaning & Support Services Ltd | Administrative & support | 2015 |
| Ingram Garrett and Schofield (NI) Limited | Administrative & support | 2006 |
| Ingramcrest Holdings Ltd | Financial services | 2025 |
| Inheritance Wills & Estate Planning Ltd | Professional & scientific | 2016 |
| Iniandy Ltd | Professional & scientific | 2025 |
| Inis Caoil | Financial services | 2024 |
| Inis Developments Limited | Professional & scientific | 1999 |
| Inis Films Ltd | Information & communication | 2025 |
| Inish Education Technology Ltd | Information & communication | 2016 |
| Inish Glow Limited | Energy | 2015 |
| Inishative Windfarm Limited | Energy | 2010 |
| Inisheer Developments Ltd | Extraterritorial | 2016 |
| Inisheer Services Ltd | Real estate | 2017 |
| Inishmurray Enterprises Ltd | Wholesale & retail | 2017 |
| Inislyn Limited | Hospitality | 1995 |
| Inked Beauty Bar Ltd | Other services | 2025 |
| Inkos 2 Limited | Professional & scientific | 2020 |
| Inkreg Ltd | Professional & scientific | 2024 |