| Headhealth Therapy Ltd | Health & social care | 2025 |
| Health&Care by Bogdan Ltd | Health & social care | 2023 |
| Heat MMA Ltd | Arts & recreation | 2022 |
| Heatabrix Limited | Professional & scientific | 2014 |
| Heffron's Bar Ltd | Hospitality | 2009 |
| Help YOU Home Limited | Information & communication | 2024 |
| Heng Yuan Ltd | Hospitality | 2026 |
| Henosis Therapeutic Family Services Ltd | Health & social care | 2024 |
| HER Fashion Armoury Ltd | Wholesale & retail | 2022 |
| Hfbc Ltd | Manufacturing | 2014 |
| HFS Food Limited | Wholesale & retail | 2014 |
| Hillside Cleaning Ltd | Administrative & support | 2026 |
| Hillside Manor Management Company Ltd | Real estate | 2025 |
| Hive Engineering Systems Limited | Professional & scientific | 2025 |
| HJZ Developments Ltd | Real estate | 2015 |
| Hnbcmdcgyxgs Limited | Wholesale & retail | 2025 |
| Hnor Limited | Real estate | 2016 |
| Hollowburn Park Limited | Real estate | 2015 |
| Home-Start Antrim District | Health & social care | 2005 |
| Hood Logistics Ltd | Transport & logistics | 2026 |
| Hot Sauce Pictures Limited | Arts & recreation | 2022 |
| Hotpursuit Enterprises Limited | Water & waste | 1998 |
| House of Butlers Ltd | Real estate | 2026 |
| HOW High Inflatables Ltd | Arts & recreation | 2024 |
| HTM Catering Limited | Hospitality | 2012 |
| HUI 6688 Ltd | Hospitality | 2025 |
| Hunter Holdings (Belfast) Limited | Manufacturing | 2017 |
| Hurrells Electrical Limited | Wholesale & retail | 2012 |
| Hydepark Ireland Limited | Wholesale & retail | 2011 |
| I. F. S. Courier Express Ltd | Transport & logistics | 1998 |
| Iconi Software Limited | Information & communication | 2000 |
| Ifod Consultancy Services Limited | Information & communication | 2023 |
| IFS Contract Services Limited | Transport & logistics | 1999 |
| IFS Global Logistics Ltd | Transport & logistics | 1971 |
| Ifychux Medical Services Ltd | Health & social care | 2024 |
| Imperial City Randalstown Ltd | Hospitality | 2014 |
| Indian Masala (Ballymena) Limited | Hospitality | 2018 |
| Industrial Floor Prepping Limited | Construction | 2019 |
| Infraex Ltd | Information & communication | 2026 |
| Ingleford Developments Ltd | Construction | 2003 |
| INNOV8 Gym (Warrenpoint) Ltd | Arts & recreation | 2025 |
| INNOV8 Gym Banbridge Ltd | Arts & recreation | 2026 |
| INNOV8 Gym Ltd | Arts & recreation | 2024 |
| Innovate (IE) Limited | Administrative & support | 2015 |
| Integrated Health Care Group Ltd | Health & social care | 2025 |
| Intelibuild Limited | Construction | 2016 |
| Intelibus Limited | Wholesale & retail | 2024 |
| Invictus Souls Limited | Health & social care | 2021 |
| Ireland Agents Ltd | Wholesale & retail | 2020 |
| Ireland by Anna Ltd | Administrative & support | 2019 |
| Ireland Freight (Forwarding) Services Ltd. | Transport & logistics | 2009 |
| Ireland Freight (Road) Services Limited | Transport & logistics | 1967 |
| Ireland Freight Services (U.K.) Limited | Professional & scientific | 1972 |
| Iron Tree Bespoke Ltd | Manufacturing | 2025 |
| Island Property Rental Limited | Real estate | 2020 |
| Islandbawn Stores Limited | Wholesale & retail | 1987 |
| Islandreagh Apartment Management (Number 3) Company Limited | Households | 2005 |
| Isopod Modular Limited | Manufacturing | 2022 |
| Izayn Studio Ltd | Information & communication | 2022 |
| IZY & LUK Property Ltd | Households | 2024 |
| J B Fabrications (N.I.) Limited | Manufacturing | 2022 |
| J.&J.S.Property Ltd | Real estate | 2020 |
| J.J. Properties (Antrim) Limited | Administrative & support | 1996 |
| Jackson Poultry Ltd | Agriculture & fishing | 2013 |
| Jalex Farms Limited | Agriculture & fishing | 2017 |
| Jalex Livestock Ltd | Agriculture & fishing | 2026 |
| JAM International Studies Academy Ltd | Education | 2019 |
| Jamdac Developments Limited | Construction | 2016 |
| James Kernohan & Sons Limited | Wholesale & retail | 2007 |
| James Robb and SON Limited | Construction | 2018 |
| James' Garden and Property Maintenance Ltd | Administrative & support | 2025 |
| Jans Holding Limited | Financial services | 2021 |
| Jans Lifestyle Limited | Manufacturing | 2021 |
| Jans Storage Limited | Real estate | 2017 |
| Japram Property PVT Limited | Real estate | 2021 |
| JAQ Fulfilment Ltd | Transport & logistics | 2021 |
| JAQ Group Holdings Limited | Financial services | 2023 |
| JAQ Group Properties Limited | Real estate | 2023 |
| Javed Genesis Limited | Wholesale & retail | 2024 |
| JC Agri & Plant Services Limited | Manufacturing | 2024 |
| JC Media Management Limited | Information & communication | 2025 |
| JCO Commerce Ltd | Wholesale & retail | 2023 |
| JE Emporium Ltd | Wholesale & retail | 2017 |
| Jenkins Foods Limited | Hospitality | 2005 |
| JGP Trade Ltd | Other services | 2023 |
| JIK JIK Limited | Financial services | 2024 |
| JMC Consulting Ltd | Administrative & support | 2025 |
| Jmck Investments Ltd | Real estate | 2023 |
| JMM Rally Cars Limited | Arts & recreation | 2024 |
| JMO Limited | Information & communication | 2025 |
| JNA Brands Ltd | Wholesale & retail | 2024 |
| Joan Henderson Education Mentor Ltd | Education | 2018 |
| John Barr Cars Limited | Wholesale & retail | 2004 |
| John H. Place (Steels) Limited | Wholesale & retail | 2004 |
| John Mulholland Motors Limited | Wholesale & retail | 2000 |
| John Stanley Property Ltd | Real estate | 2016 |
| Jojo Mechanical Repairs Ltd | Administrative & support | 2016 |
| Joli Ventures Limited | Wholesale & retail | 2022 |
| Jonac Property Group Ltd | Real estate | 2025 |
| Jonny Hanson Ventures Limited | Information & communication | 2023 |