| I-Covers 2019 (NI) Ltd | Other services | 2019 |
| I-Viuc Limited | Manufacturing | 2024 |
| I.T. Generalists Ltd | Information & communication | 2020 |
| I.Z. Management Ltd | Professional & scientific | 2025 |
| IAN James Craig Ltd | Wholesale & retail | 2024 |
| IAN Newell Holdings Limited | Financial services | 2023 |
| IAN Stewart Services Ltd | Construction | 2015 |
| Iberian Global Property Ltd | Real estate | 2025 |
| Icatu Newry Ltd | Hospitality | 2025 |
| Icmq Contracts Ltd | Construction | 2016 |
| Icon Hair and Beauty Limited | Other services | 2017 |
| Icon Trading Limited | Real estate | 2026 |
| Iconic Accessories Ireland Ltd | Wholesale & retail | 2023 |
| Iconic Creations Ltd | Wholesale & retail | 2025 |
| Iconic Sign Systems Ltd | Manufacturing | 2005 |
| Idea Shelf Limited | Information & communication | 2016 |
| Ideal Capital Distribution Ltd | Professional & scientific | 2018 |
| Ideal Hardware Supplies Limited | Wholesale & retail | 2010 |
| Ideal Window Automation Systems Limited | Construction | 2004 |
| Identity Exploration Ltd | Professional & scientific | 2005 |
| Idig Group Limited | Construction | 2025 |
| Ifenestration Ltd | Construction | 2015 |
| Ifol Bricks Ltd | Wholesale & retail | 2023 |
| IG Elements Ltd | Manufacturing | 2011 |
| Igneous Management Ltd | Real estate | 2021 |
| Ihsg Limited | Hospitality | 2023 |
| Iicm Ltd | Education | 2024 |
| IKO Transport Ltd | Transport & logistics | 2022 |
| Ikozengua Technologies Ltd | Wholesale & retail | 2014 |
| IL Drew Ltd | Transport & logistics | 2021 |
| Ilene Limited | Agriculture & fishing | 2005 |
| Ilford Park Management Co Ltd | Households | 2015 |
| Illuminate International LP | | 2018 |
| Ilyinski Holdings Limited | Health & social care | 2013 |
| Ilyinski Pain Clinic | Health & social care | 2013 |
| IM3 (UK) Limited | Manufacturing | 2019 |
| Imbolg Limited | Information & communication | 2024 |
| Imexco Sales L.P. | | 2017 |
| Imirt.Work Ltd | Professional & scientific | 2025 |
| Impact Accident Repair Centre Ltd | Wholesale & retail | 2014 |
| Impact Retail Systems Ltd | Manufacturing | 2014 |
| Imperial Blinds and Shutters Limited | Manufacturing | 2023 |
| Imperial Joinery Ltd | Manufacturing | 2024 |
| Import Experts Ireland Ltd | Wholesale & retail | 2025 |
| Importcross L.P. | | 2017 |
| Imran Sharif | Health & social care | 2012 |
| Imsolo Ltd | Information & communication | 2022 |
| Includit Ltd | Construction | 2023 |
| Incont Trade Ltd | Wholesale & retail | 2024 |
| Independent Pictures (NI) Limited | Information & communication | 2007 |
| Indonet Ventures L.P. | | 2017 |
| Industrial Distribution & Controls Limited | Manufacturing | 2006 |
| Industrial Parts Search Service LP | | 2017 |
| Industry Training Limited | Education | 2024 |
| Inertia Gymnastics Academy Ltd | Education | 2023 |
| Inet Computer Solutions NI Ltd | Administrative & support | 2021 |
| Infinite Capital Enterprises Limited | Other services | 2024 |
| Infinite Life Solutions Ltd | Health & social care | 2016 |
| Infinite Signs & Design Limited | Manufacturing | 2019 |
| Infinity Channel Swimming Ltd | Real estate | 2015 |
| Infinity Swim Academy Ltd | Education | 2016 |
| INFORM3 (NI) Ltd | Administrative & support | 2019 |
| Infowise Consulting Limited | Information & communication | 2011 |
| Ingram Contracts Ltd | Construction | 2021 |
| Inishowen Limited | Professional & scientific | 2002 |
| Inkt Trading Ltd | Wholesale & retail | 2013 |
| Inland and Coastal Marina Systems UK Ltd | Construction | 2011 |
| Inner Angel Health Ltd | Health & social care | 2025 |
| INNOV8 Fitness Limited | Arts & recreation | 2024 |
| Inor Limited | Wholesale & retail | 2026 |
| Insane Perfumes Ltd | Wholesale & retail | 2025 |
| Insights ISX4 Global Holdings Limited | Professional & scientific | 2020 |
| Insights T/A ISX4 Ltd | Information & communication | 2018 |
| Inspire Saval | Arts & recreation | 2022 |
| Inspirus Sports Management Ltd | Arts & recreation | 2019 |
| Insulation Plastering Systems Ltd | Construction | 2018 |
| Insulation Solutions Ireland Ltd | Construction | 2023 |
| Integistics Limited | Information & communication | 2025 |
| Integrated Construction Consultants Ltd | Professional & scientific | 2017 |
| Integrity Security (NI) Ltd | Administrative & support | 2023 |
| Interaero L.P. | | 2016 |
| Interiors GP NI Limited | Construction | 2025 |
| International FOG Association Ltd | Professional & scientific | 2010 |
| Interquest L.P. | | 2017 |
| Invader Concert Promotion L.P. | | 2017 |
| Inver Developments Limited | Real estate | 2023 |
| Investmax L.P. | | 2016 |
| Inveterate Ltd | Real estate | 2017 |
| IOM Ltd | Real estate | 2024 |
| Iona Electrics Limited | Energy | 2013 |
| Iona Properties Limited | Construction | 1965 |
| IOS Construction Projects Limited | Construction | 2014 |
| Ipet Wash Ltd | Administrative & support | 2023 |
| IQR Industrial L.P. | | 2017 |
| Ireland Beverage Group Ltd | Financial services | 2015 |
| Ireland Craft Beverages Ltd | Wholesale & retail | 2014 |
| Irish GAS Services Ltd | Construction | 2015 |
| Irish Guard & Offshore Services Limited | Administrative & support | 2025 |
| Irish Mowers Ltd | Wholesale & retail | 2020 |
| Irish Shopper Ltd | Wholesale & retail | 2006 |