| Herbie Paws Dog Grooming Limited | Agriculture & fishing | 2023 |
| Heritage Experience Ltd | Information & communication | 2012 |
| HES (N.I) Ltd | Agriculture & fishing | 2025 |
| Hesketh Works Ltd | Manufacturing | 2019 |
| Hillmount House Conferences & Events Ltd | Administrative & support | 2021 |
| Hillmount Ltd | Hospitality | 2014 |
| Hills Financial Planning Group Limited | Financial services | 2020 |
| Hills Insurance & Financial Services Ltd | Financial services | 2002 |
| Hills Insurance Services Ltd | Financial services | 2003 |
| Holiday Hotspot Ltd | Administrative & support | 2019 |
| Home & Garden Joinery (N.I.) Ltd | Construction | 2026 |
| Home From Home Sitters Ltd | Health & social care | 2026 |
| Home Hub Belfast C.I.C. | Education | 2021 |
| Homestart Properties Ltd | Real estate | 2023 |
| Hope House Ireland Ltd | Health & social care | 2025 |
| HR Mechanical Solutions Ltd | Construction | 2019 |
| Hunter Berkeley Ltd | Real estate | 2014 |
| Hunters Berkeley LLP | | 2022 |
| IAN Davidson Fabrication Ltd | Manufacturing | 2013 |
| Ias-Aerospace Limited | Professional & scientific | 2013 |
| ID Services (N.I.) Ltd | Other services | 2021 |
| IG Engineering (N.I.) Ltd | Manufacturing | 2025 |
| Imaj Turkish Barber Ltd | Other services | 2017 |
| Inception Equipe Limited | Manufacturing | 2014 |
| Indian Kitchen Larne Ltd | Hospitality | 2019 |
| Inisheer Ltd | Extraterritorial | 2014 |
| Innovative Automated Solutions Ltd | Professional & scientific | 2011 |
| Intermatic Manufacturing Limited | Manufacturing | 1983 |
| Inver Coaches Limited | Transport & logistics | 2018 |
| Irish Green AI Developements Limited | Information & communication | 2025 |
| Island Mill Limited | Wholesale & retail | 2016 |
| Island Safety Specialists Limited | Manufacturing | 2014 |
| Islandmagee Energy Hub Limited | Energy | 2018 |
| Islandview Engineering Services Ltd | Professional & scientific | 2021 |
| Ivybrook Enterprises Ltd | Professional & scientific | 2023 |
| J Lewis Transport Ltd | Construction | 2018 |
| J Long & SON Ltd | Wholesale & retail | 2009 |
| J W Mcninch LLP | | 2026 |
| J.K.S (Magheramorne Estate) Ltd | Hospitality | 2020 |
| J.T.Eng Limited | Administrative & support | 2023 |
| JAC Associates Ltd | Health & social care | 2011 |
| Jacj Limited | Households | 2024 |
| James Aicken Autos Ltd | Wholesale & retail | 2025 |
| Jane's Kitchen Limited | Hospitality | 2012 |
| Janz Estates Limited | Real estate | 2021 |
| JAV Consulting Ltd | Professional & scientific | 2020 |
| JB Home Solutions Ltd | Wholesale & retail | 2023 |
| JCS Kitchen Solutions Ltd | Construction | 2022 |
| JD Engineering (N.I.) Ltd | Manufacturing | 2018 |
| Jdhood Investments Ltd | Financial services | 2021 |
| JDM Steelworks Ltd | Manufacturing | 2025 |
| Jennings Bakery Ltd | Manufacturing | 2017 |
| Jensin Ltd | Hospitality | 2012 |
| Jettech Global Ltd | Manufacturing | 2018 |
| JGB Vent Ltd | Professional & scientific | 2023 |
| JGF Enterprises Ltd | Wholesale & retail | 2021 |
| JGF Investments Ltd | Construction | 2023 |
| JGF-10 Ltd | Extraterritorial | 2024 |
| JGF-12 Ltd | Extraterritorial | 2024 |
| JGF-13 Ltd | Extraterritorial | 2024 |
| JGF-14 Ltd | Extraterritorial | 2024 |
| JGF-15 Ltd | Extraterritorial | 2024 |
| JGF-16 Ltd | Extraterritorial | 2024 |
| JGF-17 Ltd | Extraterritorial | 2024 |
| JGF-6 Ltd | Extraterritorial | 2024 |
| JGF-7 Ltd | Extraterritorial | 2024 |
| JGF-8 Ltd | Extraterritorial | 2024 |
| Jhfs Services Ltd | Financial services | 2017 |
| Jillian M Saulters Ltd | Health & social care | 2010 |
| JJC Haulage Ltd | Transport & logistics | 2017 |
| JKS (N.I.) Ltd | Manufacturing | 2025 |
| JL Services (Global) UK Ltd | Professional & scientific | 2022 |
| JM Servicess Ltd | Construction | 2026 |
| JMC Electrical (NI) Ltd | Construction | 2012 |
| Jmck Tailored Plastering Ltd | Construction | 2025 |
| JMJ Capital Limited | Financial services | 2018 |
| JN Leisure Ltd | Arts & recreation | 2016 |
| Jobling Planning and Environment Limited | Professional & scientific | 2014 |
| John Mcloughlin & SON (Shipping) Limited | Transport & logistics | 1979 |
| Johnny Mahood Engineering Ltd | Professional & scientific | 2021 |
| Joshua Hayes Car Sales Ltd | Wholesale & retail | 2016 |
| JOW Rubber Co Larne Ltd | Extraterritorial | 2018 |
| JSG Groundworx Ltd | Extraterritorial | 2018 |
| Juiceweb.Site Ltd | Professional & scientific | 2025 |
| Just Active Injury Clinic Ltd | Extraterritorial | 2017 |
| K Larne Ltd | Hospitality | 2022 |
| K.L.K Aerospace Ltd | Manufacturing | 2019 |
| K9NI Manufacturing Ltd | Manufacturing | 2021 |
| KAR Service Ltd | Wholesale & retail | 2024 |
| Kathleen Mckillion Consulting Limited | Professional & scientific | 2024 |
| Katq Ltd | Manufacturing | 2020 |
| KBD (N.I.) Ltd | Professional & scientific | 2023 |
| KEN Falconer.Com Ltd | Health & social care | 2017 |
| Kenkay Kitchen Design Ltd | Manufacturing | 2024 |
| Kerragh Rock Services Ltd | Extraterritorial | 2020 |
| Kilmegan Investments Limited | Health & social care | 2008 |
| Kilwaughter 520 Limited | Education | 2019 |
| Kilwaughter Holdings Ltd | Financial services | 2014 |
| Kilwaughter Mews Management Company Ltd | Households | 2005 |
| Kjmac Limited | Financial services | 2022 |