| Immersive Golf Ltd | Administrative & support | 2020 |
| Impaired Living Limited | Health & social care | 2012 |
| Ingledene Developments Limited | Construction | 2018 |
| Innis Holdings Ltd | Real estate | 2024 |
| Innovative Enviro Solutions Ltd | Administrative & support | 2025 |
| Inside-Out Environment Design Consultants Limited | Professional & scientific | 2018 |
| Intelligent Hospitality Design Ltd | Wholesale & retail | 2022 |
| Intelligent Maintenance Ltd | Construction | 2023 |
| Intelligent Operations Ltd | Professional & scientific | 2021 |
| Inter-Ethnic Forum (MID and East Antrim) | Education | 2007 |
| IPS Cubicle (NI) Limited | Construction | 2014 |
| Irinshe Ltd | Health & social care | 2025 |
| Irish Moiled Cattle Society | Agriculture & fishing | 1998 |
| Irons Home Bakery Ltd | Manufacturing | 2021 |
| Islandcorr Transport Limited | Transport & logistics | 2021 |
| Islandpoint Studios Ltd | Other services | 2010 |
| Islandreagh Apartment Management Company Limited | Households | 2005 |
| Islandreagh Open Space Management Company Limited | Extraterritorial | 2005 |
| IT Happens Ltd. | Hospitality | 2016 |
| Ives EU REP Ltd | Professional & scientific | 2025 |
| IVL IRE 001 Ltd | Energy | 2023 |
| IVY & Gold Limited | Manufacturing | 2020 |
| J & B Morrow Ltd | Wholesale & retail | 2007 |
| J & J Law Kitchen Limited | Hospitality | 2025 |
| J & S Mckee Ltd | Construction | 2010 |
| J B Furniture Carcasses Limited | Manufacturing | 2025 |
| J Baxter Haulage Ltd | Transport & logistics | 2020 |
| J C Harkness & Co | Wholesale & retail | 2009 |
| J H Painting and Cleaning Contractors Limited | Construction | 2012 |
| J M F Properties Limited | Wholesale & retail | 2001 |
| J MAC (N.I.) Limited | Water & waste | 2020 |
| J Millar Contracts Ltd | Construction | 2018 |
| J R Wilson Construction Limited | Construction | 2016 |
| J&R Fuels Limited | Wholesale & retail | 2018 |
| J-Sibs Ltd | Wholesale & retail | 2023 |
| J. a. Mcclelland & Sons (Auctioneers), Limited | Real estate | 1955 |
| J. Kyle Motor Spares Limited | Wholesale & retail | 2025 |
| J.A. Mcclelland & Sons (Estate Agents) Limited | Real estate | 1979 |
| J.A. Mcnicholl & Company Limited | Professional & scientific | 1999 |
| J.F. & H. Dowds Limited | Construction | 1997 |
| J.I.A. Construction Ltd | Construction | 2009 |
| J.K.S (Investments N.I.) Ltd | Real estate | 2025 |
| J.K.S. Property Holdings (N.I.) Ltd | Financial services | 2026 |
| J.N.K. Components Limited | Wholesale & retail | 1984 |
| J.O.B. Contracts Ltd | Construction | 2018 |
| J.P. Painting Contractors (NI) Limited | Construction | 2014 |
| J26 Car Sales Ltd | Wholesale & retail | 2024 |
| JA Vikings Barber Shop Ltd | Other services | 2025 |
| Jack Armstrong Developments Limited | Wholesale & retail | 1997 |
| Jack Ryan Ltd | Real estate | 2004 |
| Jack Ryan Power Limited | Wholesale & retail | 2017 |
| Jackson Steveley Property Limited | Real estate | 2025 |
| Jacob's Kitchen Limited | Hospitality | 2024 |
| JAD Property & Developments Ltd | Construction | 2026 |
| James a Scullion Limited | Construction | 2001 |
| James Mckeown Accident Repair Limited | Wholesale & retail | 2018 |
| James Mcneill Grocery Limited | Wholesale & retail | 2004 |
| James Moore (Ballymena) Limited | Extraterritorial | 1976 |
| James O'Rawe | Agriculture & fishing | 2019 |
| James Skincare (UK) Ltd | Other services | 2020 |
| James Stevenson (Quarries) Limited | Mining & quarrying | 1991 |
| James Tolland Investments Limited | Financial services | 1988 |
| Jamie Sloan Racing Ltd | Arts & recreation | 2022 |
| Janines Pooch Parlour NI Ltd | Other services | 2024 |
| Japp Transmissions Limited | Construction | 2018 |
| JB Aluminium Ltd | Manufacturing | 2023 |
| JB Door Systems Ltd | Construction | 2017 |
| Jcgr Ltd | Construction | 2020 |
| Jchc Ltd | Extraterritorial | 2009 |
| JD Graham Ltd | Agriculture & fishing | 2014 |
| Jdowl Enterprises Ltd | Wholesale & retail | 2024 |
| Jedp Ltd | Real estate | 2019 |
| Jemca Properties Ltd | Real estate | 2020 |
| Jennybristow.Com Ltd | Extraterritorial | 2007 |
| JES Sealants Ltd | Construction | 2025 |
| Jetdog Pet Products Ltd | Manufacturing | 2024 |
| JF Joinery Limited | Construction | 2012 |
| JFI Limited | Professional & scientific | 2014 |
| JH & a Davison Ltd | Agriculture & fishing | 2016 |
| Jimcater Limited | Hospitality | 2017 |
| JJ Soft Surfacing Ltd | Construction | 2022 |
| JKC Electrics Ltd | Construction | 2013 |
| JKM Farms Ltd | Agriculture & fishing | 2026 |
| JLG Racing Limited | Arts & recreation | 2022 |
| JLM Payroll NI Limited | Professional & scientific | 2025 |
| Jlove Healthcare Services Limited | Health & social care | 2022 |
| JM Autos NI Ltd | Wholesale & retail | 2019 |
| JMA Electrical Ltd | Construction | 2015 |
| JMA Holdings Ltd | Professional & scientific | 2017 |
| Jmac Plant Hire Limited | Construction | 2021 |
| Jmcc Health & Fitness Limited | Arts & recreation | 2021 |
| Jmcniron Ltd | Construction | 2020 |
| JMD Construction Ltd | Construction | 1999 |
| JMF Automotive NI Limited | Wholesale & retail | 2025 |
| JMT Contracts Ltd | Construction | 2021 |
| JOC Engineering Ltd | Professional & scientific | 2021 |
| JOE Hunter & Sons Ltd | Construction | 2007 |
| John & Sally's Limited | Hospitality | 2025 |
| John Dickey Ltd | Real estate | 2015 |
| John Mcmanus Limited | Administrative & support | 2012 |