| Inlu Ltd | Information & communication | 2023 |
| Innalabs UK Limited | Wholesale & retail | 2015 |
| Innate Film Productions Ltd | Information & communication | 2025 |
| Innate Films Limited | Information & communication | 2019 |
| Inner Smile Ireland Ltd | Health & social care | 2014 |
| Inner Stream Ltd | Professional & scientific | 2004 |
| Innerworkings (NI) Limited | Manufacturing | 2012 |
| Innetwork Technology Limited | Information & communication | 2026 |
| Innisfayle House Limited | Extraterritorial | 1975 |
| INNO3 Ltd | Professional & scientific | 2022 |
| Innocap UK Limited | Water & waste | 2023 |
| Innotools Technology Limited | Wholesale & retail | 2025 |
| INNOV8 Workspace Solutions Limited | Wholesale & retail | 2020 |
| Innova Developments (NI) Limited | Real estate | 2015 |
| Innova Technologies Limited | Information & communication | 2022 |
| Innovaflex Ltd | Administrative & support | 2018 |
| Innovascope Limited | Education | 2025 |
| Innovate Social Ltd | Professional & scientific | 2023 |
| Innovatex Limited | Extraterritorial | 2016 |
| Innovation Ulster Limited | Other services | 1997 |
| Innovationx Holdings Limited | Other services | 2022 |
| Innovative Engineering Services Ltd | Administrative & support | 2023 |
| Innovative Furniture Ltd | Manufacturing | 2018 |
| Innovative Power Generation Ltd | Manufacturing | 2019 |
| Innovative Property Developments Limited | Construction | 2017 |
| Innovative Solutions for the Scholarly Research Community Limited | Information & communication | 2013 |
| Innovative Workplace Solutions Ltd | Information & communication | 2022 |
| Innovativeecomsolutions Ltd | Wholesale & retail | 2026 |
| Innovativeidays Ltd | Information & communication | 2014 |
| Innovia Advisory Limited | Professional & scientific | 2017 |
| Inntown Group Limited | Financial services | 2026 |
| Inntown Living R2R Limited | Hospitality | 2026 |
| Inntown Management Ltd | Real estate | 2021 |
| Inotee Group Limited | Administrative & support | 2022 |
| INOV8 Systems Limited | Manufacturing | 2016 |
| Inovati Limited | Wholesale & retail | 2021 |
| Inplay Iptv Ltd | Information & communication | 2008 |
| Inpost Northern Ireland Limited | Wholesale & retail | 2006 |
| Inrito Limited | Professional & scientific | 2001 |
| Insec N.Ireland Ltd | Administrative & support | 2010 |
| Inside OUT Design Consultants Limited | Professional & scientific | 2024 |
| Inside Voice Ltd | Manufacturing | 2020 |
| Insight Accessibility Limited | Education | 2006 |
| Insight Accounting Systems Ltd | Information & communication | 2017 |
| Insight Mystery Shopping Ltd | Professional & scientific | 2013 |
| Inspire Business Centre Ltd | Real estate | 1992 |
| Inspire by Design Kitchens Limited | Manufacturing | 2017 |
| Inspire Education and Business Consulting Ltd | Education | 2013 |
| Inspire Flavours Ltd | Manufacturing | 2016 |
| Inspire Group (N.I.) Ltd | Information & communication | 2022 |
| Inspire Loyalty Ltd | Information & communication | 2018 |
| Inspire Stationery Ltd | Wholesale & retail | 2026 |
| Inspire Wellbeing | Health & social care | 1991 |
| Inspired Talents FC Ltd | Arts & recreation | 2025 |
| Inspiring View Limited | Professional & scientific | 2020 |
| Inst Hockey Limited | Arts & recreation | 2005 |
| Instadetect Ltd. | Wholesale & retail | 2016 |
| Instagiv Limited | Other services | 2009 |
| Instant Heirlooms Ltd | Manufacturing | 2016 |
| Instil Holdings Limited | Financial services | 2024 |
| Instil Software Limited | Information & communication | 2005 |
| Institute of Accounting Technicians in Ireland Limited - the | | 1984 |
| Institute of Data Ltd | Education | 2023 |
| Instorage Ltd | Real estate | 2011 |
| Instyl Ltd | Wholesale & retail | 2023 |
| Instyle Maple Limited | Wholesale & retail | 2024 |
| Insurancecheck Limited | Financial services | 2003 |
| Insure I Limited | Financial services | 2009 |
| Intact Insurance | | 2019 |
| Intec Design Ltd | Professional & scientific | 2022 |
| Intech Global L.P. | | 2018 |
| Integra Psychology Limited | Education | 2026 |
| Integral Project Services Ltd | Information & communication | 2008 |
| Integrated Education Fund | Professional & scientific | 2016 |
| Integrated Neuroaffirmative Care CIC | Health & social care | 2026 |
| Integrated Services Design Limited | Professional & scientific | 2000 |
| Integriqa (Holdings) Limited | Information & communication | 2025 |
| Integriqa Ltd | Administrative & support | 2025 |
| Integrity PM Ltd | Professional & scientific | 2025 |
| Integrity-Ni Ltd | Professional & scientific | 2011 |
| Intelesens Limited | Manufacturing | 2000 |
| Intelligence Software Ltd | Information & communication | 2005 |
| Intelligent Asphalt and Tarmacing Solutions Ltd | Construction | 2018 |
| Intelligent Facility Solutions (N.I.) Limited | Administrative & support | 2024 |
| Intelligent Green Energy Limited | Energy | 2016 |
| Intelligent Green Energy Two Limited | Energy | 2016 |
| Intellimate Ltd | Information & communication | 2024 |
| Intent Belfast Limited | Arts & recreation | 2021 |
| Inter Dealer Movements (NI) Ltd | Transport & logistics | 2011 |
| Inter Haulage Ltd | Transport & logistics | 2018 |
| Inter State Sports & Academics Ltd | Transport & logistics | 2020 |
| Intercity Agencies Limited | Wholesale & retail | 2011 |
| Intercity Investigations Limited | Administrative & support | 2025 |
| Interclean Hygiene & Cleaning Supplies Limited | Wholesale & retail | 1994 |
| Intercomm Ireland | Other services | 2004 |
| Interesting Electrical Devices Ltd | Wholesale & retail | 2011 |
| Interfrigo Limited | Manufacturing | 1973 |
| Interim Total Solutions Ltd | Construction | 2025 |
| Interior 360 Design Limited | Wholesale & retail | 2014 |
| Interior 360 Ltd | Wholesale & retail | 2003 |