| Imaginationderry Limited | Arts & recreation | 2026 |
| Immediate Homes (N.I.) Ltd | Administrative & support | 2020 |
| Impact Garage Supplies Ltd | Wholesale & retail | 2020 |
| IN Your Element Ltd | Professional & scientific | 2013 |
| IN Your Space Circus Ltd | Arts & recreation | 2004 |
| Inbound Studios Limited | Professional & scientific | 2019 |
| Incharge HQ Limited | Information & communication | 2026 |
| Inchinagh Electrical Ltd | Construction | 2022 |
| Infrasphere Global Technologies Ltd | Information & communication | 2024 |
| Inishowen Creels Limited | Manufacturing | 2019 |
| Inner City Buildings Preservation Trust | Other services | 2012 |
| Innovative Management Systems Limited | Information & communication | 2006 |
| Innvillagesecurity Limited | Administrative & support | 2018 |
| Inox Engineering & Powdercoating Ltd | Professional & scientific | 2020 |
| Insight-Adhd Ltd | Health & social care | 2026 |
| Instant Promotion Limited | Hospitality | 1990 |
| Integrated Power Systems Ltd | Professional & scientific | 2019 |
| Internet Marketing & Advertising Ltd | Administrative & support | 2011 |
| Investmd Limited | Real estate | 2025 |
| Investments 65 - 67 Limited | Real estate | 2019 |
| Invistra Ltd | Information & communication | 2026 |
| IP Logic Ltd | Wholesale & retail | 2012 |
| Iringa TOO Limited | Financial services | 2019 |
| Irish Artisan Cheese Provisions Ltd | Wholesale & retail | 2025 |
| Irish Guild of NLP and Hypnotherapy Practitioners and Trainers Ltd | Professional & scientific | 2021 |
| Irish Masters (Old School Events) Limited | Information & communication | 2025 |
| Irish Street Youth and Community Association | Education | 2017 |
| Irwin and Sons Engineering Ltd | Financial services | 2025 |
| Irwin Car Sales Ltd | Wholesale & retail | 2024 |
| Island Church Ltd | Other services | 2021 |
| Istanbul Turkish Restaurant Ltd | Hospitality | 2021 |
| IT Works Connection Ltd | Professional & scientific | 2025 |
| J & C Bars Ltd | Hospitality | 2016 |
| J & D Drinks Ltd | Hospitality | 2022 |
| J & H Contracts Limited | Construction | 2018 |
| J & R Snodgrass Limited | Construction | 2024 |
| J C M S Investments Limited | Construction | 2015 |
| J Curran Accountants Ltd | Professional & scientific | 2022 |
| J Curran Electrical Ltd | Construction | 2024 |
| J D a Electrics Ltd | Construction | 2000 |
| J G Roundstone Limited | Real estate | 2018 |
| J J Mcgowan Flooring Limited | Construction | 2022 |
| J M N Retailers Ltd | Wholesale & retail | 2014 |
| J Property Investment Group Ltd | Real estate | 2026 |
| J Russell Properties Ltd | Real estate | 2006 |
| J S MC Contracting and Sales Ltd. | Agriculture & fishing | 2017 |
| J Wealth Investment Group Ltd | Real estate | 2025 |
| J&A Prime Properties Ltd | Real estate | 2024 |
| J&E Vending Ltd | Wholesale & retail | 2026 |
| J. Peoples Distribution Ltd | Transport & logistics | 2003 |
| J. Young & Sons Limited | Administrative & support | 1996 |
| J.A. Mchugh | Extraterritorial | 1975 |
| J.Abel Transport Ltd | Transport & logistics | 2020 |
| J3 Business Group Ltd | Real estate | 2025 |
| Jaair Consulting Limited | Administrative & support | 2011 |
| Jacksons Catering Equipment Limited | Wholesale & retail | 2020 |
| Jacsi Properties Limited | Construction | 2005 |
| Jada Enterprises Ltd | Wholesale & retail | 2024 |
| Jahan Enterprises Ltd | Transport & logistics | 2019 |
| Jaked Limited | Real estate | 2025 |
| James a. Mchugh Limited | Transport & logistics | 2001 |
| James Eakin (Tractors) Limited | Real estate | 1972 |
| James O'Hara Homes Limited | Construction | 2016 |
| James Parkhill Construction Limited | Construction | 2021 |
| James Smith (N.W.) Ltd | Other services | 2019 |
| James Street Properties Ltd | Real estate | 2019 |
| Jammt Medical Ltd | Health & social care | 2018 |
| Jarp Property Services Limited | Hospitality | 2014 |
| Jaspers to Go Limited | Hospitality | 2026 |
| JB3 Mobile Limited | Wholesale & retail | 2012 |
| JC Designstudio Ltd | Professional & scientific | 2019 |
| JC Drylining Limited | Construction | 2017 |
| JCD Derry Limited | Manufacturing | 2024 |
| JCK Construction Ltd | Construction | 2026 |
| JCO Consulting Ltd | Information & communication | 2023 |
| JCS Venture Ltd | Wholesale & retail | 2023 |
| JD Joinery & PVC Ltd | Construction | 2024 |
| Jdlpartitions Ltd | Construction | 2026 |
| JDR Civil Engineering Limited | Construction | 2015 |
| JDR Plant & Tool Hire Limited | Administrative & support | 2020 |
| Jemma @ Vanity Ltd | Other services | 2023 |
| Jeneen Ltd | Hospitality | 2014 |
| Jeremy Arthur Limited | Real estate | 2005 |
| Jeremy Johnston Limited | Health & social care | 2008 |
| Jgfc Ltd | Information & communication | 2025 |
| Jgtf Enterprises Ltd | Professional & scientific | 2010 |
| JH Stress Engineering Ltd | Professional & scientific | 2024 |
| JHT Foods Ltd | Wholesale & retail | 2019 |
| JHT Smith Holdings Ltd | Wholesale & retail | 2025 |
| Jiji Wong Limited | Manufacturing | 2024 |
| Jind Food Ltd | Hospitality | 2025 |
| Jireh Biomedical Ltd | Professional & scientific | 2023 |
| JJ & LA Ltd | Financial services | 2005 |
| JJ Coyle Limited | Wholesale & retail | 2003 |
| JJ Joinery Enterprises Limited | Construction | 2022 |
| JJM Developments (NI) Ltd | Real estate | 2015 |
| Jjsk Investments Limited | Financial services | 2014 |
| JLM Eatery Ltd | Hospitality | 2025 |
| Jlrc Derry Limited | Real estate | 2020 |
| JLX Arch Ltd | Professional & scientific | 2022 |