| Hillside Investments Ltd | Real estate | 1996 |
| Hilltop Living Ltd | Information & communication | 2025 |
| Hilltop Turbine Ltd | Energy | 2015 |
| Hillview Property Developments Limited | | 2005 |
| Hive Key Property Ltd | Real estate | 2025 |
| HK Joinery & Building Contractor Ltd | Construction | 2017 |
| Hollow Park Sand and Gravel Limited | Mining & quarrying | 2016 |
| Holmlea Construction Ltd | Construction | 2012 |
| Home Cosmetics Ltd | Wholesale & retail | 2020 |
| Homebawn Limited | Education | 2024 |
| Hope Magherafelt | Hospitality | 2015 |
| HSF Group Transport Ltd | Transport & logistics | 2024 |
| HTY Holdings Ltd | Manufacturing | 2025 |
| Humboldt Properties Limited | Real estate | 2025 |
| Hunter Tractors Limited | Manufacturing | 2021 |
| Hurl Construction Services Ltd | Construction | 2015 |
| Hurley Transport Ltd | Transport & logistics | 2025 |
| Hurst Design Limited | Professional & scientific | 2024 |
| Hurst Engineering Services Ltd | Professional & scientific | 2022 |
| Hutchinson Fitness & Recovery Ltd | Education | 2026 |
| Hutton Meats Limited | Wholesale & retail | 2018 |
| Iaad NI Ltd | Administrative & support | 2022 |
| IAN Walker Contracts Ltd | Administrative & support | 2018 |
| Icontrol Building Ltd | Construction | 2016 |
| Igen Autos Ltd | Wholesale & retail | 2021 |
| IGI Associates Limited | Professional & scientific | 2021 |
| Ignite Plumbing Services (IRE) Ltd | Construction | 2021 |
| IME Electrical Services Limited | Construction | 2023 |
| Imed (NI) Limited | Professional & scientific | 2013 |
| Incrementum (Europe) Ltd | Construction | 2023 |
| Industry Pipelines Ltd | Construction | 2019 |
| Infiniphy Ltd | Information & communication | 2023 |
| Infinite Consulting Services Ltd | Professional & scientific | 2026 |
| Inglebrook Holdings Limited | Financial services | 2017 |
| Inis Carn Services Ltd | Construction | 2025 |
| Innisduff Ltd | Wholesale & retail | 2013 |
| Inova Gates Limited | Construction | 2003 |
| Insite Tours Ireland Limited | Administrative & support | 2016 |
| Insulation Centres Limited | | 2001 |
| Interpackni Ltd | Wholesale & retail | 2012 |
| Involve (NI) | Administrative & support | 2013 |
| Ionic IT Ltd | Information & communication | 2008 |
| IQ Recycling Solutions (NI) Ltd | Water & waste | 2020 |
| Irish Miles Ltd | Administrative & support | 2019 |
| Ironbit Ltd | Information & communication | 2025 |
| Island Farms NI Limited | Agriculture & fishing | 2010 |
| Itek Iphones Ltd | Wholesale & retail | 2014 |
| J & B Hamilton Limited | Construction | 2004 |
| J Deere Contracts Ltd | Construction | 2017 |
| J Hancock Businesses Ltd | Real estate | 2011 |
| J Kilpatricks Ltd | Agriculture & fishing | 2019 |
| J Mcglade Ltd | Extraterritorial | 2006 |
| J O'Hagan Contracts Limited | Construction | 2021 |
| J&Ah Ltd | Construction | 2020 |
| J&F Consultancy Ltd | Construction | 2013 |
| J&M Auto Sales Ltd | Wholesale & retail | 2016 |
| J&M Rental Property Ltd | Real estate | 2017 |
| J&M Rentals Ltd | Real estate | 2017 |
| J&O Passive Fire Solutions Limited | Construction | 2024 |
| J, Lewis & Gregg Ltd | Construction | 2023 |
| J.D. Ventilation Services Limited | Manufacturing | 2019 |
| Jaer Group Limited | Financial services | 2024 |
| Jaldma Limited | Wholesale & retail | 2012 |
| James Mcgeehan & Sons Transport Limited | Transport & logistics | 1989 |
| James Paul Properties Ltd | Real estate | 2017 |
| Java Holdings Ltd | Financial services | 2018 |
| JC Metal Roofing Ltd | Construction | 2021 |
| JCQ Electrical Ltd | Construction | 2024 |
| JCS TTT Ltd | Wholesale & retail | 2014 |
| JD Salvage Ltd | Wholesale & retail | 2023 |
| Jdas Enterprises Ltd | Mining & quarrying | 2022 |
| Jdmd Trading Company Limited | Wholesale & retail | 2023 |
| JEN Management Co Limited | Households | 2019 |
| JF Facades Ltd | Manufacturing | 2026 |
| Jfmcatering Ltd | Hospitality | 2025 |
| Jiejiejiegege Ltd | Wholesale & retail | 2025 |
| Jimhealth Ltd | Health & social care | 2026 |
| JNL Group Ltd | Construction | 2024 |
| John J Mcnally & Co Limited | Professional & scientific | 2012 |
| John J. Higgins (Holdings) Limited | Financial services | 2025 |
| John Moran & Sons Limited | Transport & logistics | 2014 |
| Johnny Doyle Limited | Manufacturing | 2024 |
| Joseph Hegarty Ltd | Construction | 2015 |
| Journey of Gentlemen Ltd | Wholesale & retail | 2023 |
| JPS Restaurants Ltd | Hospitality | 2024 |
| JQB Parts Ltd | Wholesale & retail | 2026 |
| JSB Accountancy Ltd | Professional & scientific | 2012 |
| JTA Electrical Ltd | Construction | 2021 |
| JTS Painting Contracts Ltd | Construction | 2023 |
| K & S Restaurant (2019) Ltd | Hospitality | 2019 |
| K.K.N Group Limited | Real estate | 2025 |
| Kajo Ltd | Wholesale & retail | 2024 |
| Kangen UK Ireland Ltd | Wholesale & retail | 2014 |
| Kcellars Limited | Wholesale & retail | 2015 |
| KDS Precast Installations Ltd | Construction | 2016 |
| Keenaght Custom Interiors Ltd | Manufacturing | 2015 |
| Keevan Ltd | Wholesale & retail | 2025 |
| Kell-Reagh Civils Ltd | Construction | 2024 |
| Kellson Limited | Real estate | 2012 |
| Kelly Cellars Limited | Hospitality | 2012 |