| Hillsborough Sporting GUN Club Limited | Arts & recreation | 1989 |
| Holdco EEB Limited | Financial services | 2024 |
| Holiday Nails & Spa Ltd | Other services | 2025 |
| Hollybrook Sports Cars Ltd | Wholesale & retail | 2008 |
| Hollydene Group Limited | Financial services | 2025 |
| Hollydene Holdings Ltd | Financial services | 2023 |
| Home Ventilation Solutions Ltd | Professional & scientific | 2016 |
| Horsewalk International Limited | Manufacturing | 2019 |
| Hyde Air Park Ltd | Transport & logistics | 2024 |
| Hynes Plumbing and Heating Ltd | Construction | 2018 |
| Ignite SFX Ltd | Information & communication | 2021 |
| Inspire ME Entertainment Ltd | Arts & recreation | 2023 |
| Intelligent Air Management Ltd. | Professional & scientific | 2011 |
| International Airport Taxi Company Limited | Transport & logistics | 1997 |
| International Devteam Ltd | Information & communication | 2019 |
| Intuitive CNC Ltd | Professional & scientific | 2023 |
| J W Motors Crumlin Ltd | Wholesale & retail | 2022 |
| Jacqueline Marcella Kathleen Mcdermott Limited | Extraterritorial | 2025 |
| Jade Developments Ltd | Construction | 2006 |
| Java Contracts Ltd | Professional & scientific | 2024 |
| JC Pet Food Ltd | Manufacturing | 2023 |
| Jimac Tools Ltd | Manufacturing | 2018 |
| JPM Equity Ltd | Real estate | 2023 |
| Jsat Energy Ltd | Construction | 2025 |
| Juko Coffee Ltd | Hospitality | 2025 |
| Just BE Kalm Limited | Other services | 2015 |
| Kanto Lisburn Limited | Hospitality | 2019 |
| KD Plant & Machinery Limited | Wholesale & retail | 2011 |
| KDM Commerce Ltd | Wholesale & retail | 2025 |
| KDM Joinery Ltd | Construction | 2025 |
| KE Nako Biltong Limited | Manufacturing | 2013 |
| Kennedy Joinery Ltd | Construction | 2022 |
| Kennedy Property Group Ltd | Real estate | 2026 |
| King of Chemicals Ltd | Wholesale & retail | 2025 |
| Kiss My Face Limited | Information & communication | 2025 |
| KL Mulholland Ltd | Real estate | 2020 |
| Kleopatra UK Limited | Professional & scientific | 2007 |
| Klockner Pentaplast Limited | Manufacturing | 1998 |
| KMC Optical Ltd | Health & social care | 2026 |
| Kompact Engineering Ltd | Manufacturing | 2016 |
| KP Graham & Sons Ltd | Construction | 2025 |
| KSM Farms Ltd | Agriculture & fishing | 2012 |
| L&K Global Ltd | Construction | 2023 |
| Lakeview Farm Meats Limited | Agriculture & fishing | 2010 |
| Lallo Ltd. | Information & communication | 2015 |
| Langford Lodge Engineering Company Limited | Manufacturing | 1975 |
| Langford Lodge Holdings (NI) Limited | Professional & scientific | 1959 |
| Largy Residential Ltd | Households | 2023 |
| Leptus Ltd | Wholesale & retail | 1997 |
| Lidl Northern Ireland Limited | Wholesale & retail | 2017 |
| Likespeed Limited | Wholesale & retail | 2023 |
| LJL Enterprises Limited | Hospitality | 2021 |
| LM Contracts Services Ltd | Construction | 2026 |
| LMO Estate Agents Ltd | Real estate | 2023 |
| Lock and Secure Ltd | Construction | 2023 |
| Lorcan Homes Ltd | Construction | 2012 |
| Loughshore Property Ventures Ltd | Real estate | 2024 |
| Loughside Transport & Plant Hire Ltd | Transport & logistics | 2012 |
| LTS Financial Holdings Ltd | Real estate | 2023 |
| Lunaro Living Ltd | Wholesale & retail | 2026 |
| Lurgan Road Energy Ltd | Energy | 2026 |
| Lyngrove Hill Management Company Limited | Households | 2005 |
| M B Transport (2016) Ltd | Transport & logistics | 2016 |
| M H Contracts Ltd | Construction | 2018 |
| M.G. Matics Limited | Administrative & support | 1994 |
| M.J. Woodworking Machinery Ltd | Manufacturing | 2006 |
| Mac's Accident Assist Limited | Transport & logistics | 2025 |
| Mac's Executive Travel Ltd | Transport & logistics | 2025 |
| Main Event Media Ltd | Information & communication | 2019 |
| Making 9 to 5 Ltd | Arts & recreation | 2022 |
| Mallon Consultancy Services Ltd | Professional & scientific | 2011 |
| Maplore Holdings Ltd | Real estate | 2024 |
| Marbur Properties (N.I.) Limited | Real estate | 1975 |
| Masala Bites Crumlin Limited | Hospitality | 2025 |
| Mastove Limited | Hospitality | 2011 |
| MAX Power Europe Limited | Energy | 2025 |
| Maxtracking Limited | Administrative & support | 2021 |
| MB Contracts Glenavy Ltd | Construction | 2020 |
| MCA Accountants Limited | Professional & scientific | 2015 |
| Mccomb Engineering Ltd | Manufacturing | 2008 |
| Mcconkey Property Ltd | Real estate | 2023 |
| Mcgrade Engineering Ltd | Professional & scientific | 2024 |
| MCK Rentals Ltd | Real estate | 2023 |
| Mckensholdings Ltd | Wholesale & retail | 2020 |
| Mckenzie Business Associates Ltd | Professional & scientific | 2015 |
| Mckinstry Biomass Ltd | Water & waste | 2013 |
| Mckinstry Metal Recycling Limited | Water & waste | 2017 |
| Mckinstry Skip Hire Limited | Water & waste | 2003 |
| Mckinstry Waste Services Ltd | Water & waste | 2013 |
| MCT Cars Ltd | Wholesale & retail | 2016 |
| MG Contracts (Belfast) Ltd | Construction | 2017 |
| Mill House Management Company (NI) Limited | Households | 2007 |
| Mill Mews Management Limited | Real estate | 2004 |
| MO Team Ltd | Professional & scientific | 1997 |
| Moducore Systems Ltd | Information & communication | 2025 |
| Morelli's Dismantlers Ltd | Wholesale & retail | 2022 |
| Mourne Merchandise Limited | Wholesale & retail | 2024 |
| Mpani Limited | Other services | 2006 |
| MPS Studio Ltd | Information & communication | 2019 |
| Mrcl Consultants Ltd | Information & communication | 2021 |