| Moss Contracts Ltd | Construction | 2017 |
| Moss Property Limited | Real estate | 2015 |
| Moss Tiles Limited | Wholesale & retail | 2003 |
| Moss View Potato Limited | Wholesale & retail | 2023 |
| Mosswell Engineering Ltd | Professional & scientific | 2020 |
| Motalee Investments Limited | Real estate | 1985 |
| Motion Alchemy Ltd | Information & communication | 2025 |
| Motus Fitness Ltd | Arts & recreation | 2026 |
| Mountview Retreat Limited | Real estate | 2022 |
| Mourne Safety Compliance Ltd | Professional & scientific | 2026 |
| Move Recruitment (N.I.) Limited | Administrative & support | 2024 |
| Moyheeland Limited | Wholesale & retail | 2002 |
| Moyheeland Properties Ltd | Construction | 2003 |
| Moyola Construction Limited | Construction | 2021 |
| Moyola Consulting Limited | Information & communication | 2023 |
| Moyola Eggs Ltd | Agriculture & fishing | 2025 |
| Moyola Group Limited | Professional & scientific | 2017 |
| Moyola Landscapes Limited | Administrative & support | 2017 |
| Moyola Partitions Ltd | Construction | 2019 |
| Moyola Precision Engineering Limited | Manufacturing | 1976 |
| Moyola Services Limited | Construction | 2025 |
| MPB Construction Limited | Construction | 2001 |
| MPD Furniture Ltd | Wholesale & retail | 2020 |
| MPP Lifts Limited | Manufacturing | 2021 |
| MSM Accountancy Ltd | Professional & scientific | 2018 |
| MT Building and Construction Services Ltd | Construction | 2020 |
| MTF Mouldings Limited | | 2001 |
| MU-4 Ltd | Wholesale & retail | 2018 |
| Mubm Contracts Ltd | Construction | 2017 |
| Muldoon Autoparts Ltd | Wholesale & retail | 2024 |
| Mulholland Family Holdings Ltd | Financial services | 2021 |
| Mulinderg Management Company Limited | Real estate | 2007 |
| Mullan Spraying Services Ltd | Construction | 2020 |
| Mullinsallagh 56 Limited | Construction | 2024 |
| Mullinsallagh Limited | Construction | 2008 |
| Muls (NI) Ltd | Real estate | 2014 |
| Multiple Product Designs Ltd | Professional & scientific | 2012 |
| Mupd Contracts Ltd | Construction | 2021 |
| Murray Motors Magherafelt Ltd | Wholesale & retail | 2017 |
| Muss Signage Ltd | Manufacturing | 2026 |
| MV4 Ltd | Construction | 2023 |
| Mynt-Condition Ltd | Administrative & support | 2023 |
| Mzew Limited | Information & communication | 2025 |
| N & K Pharmacy Ltd | Wholesale & retail | 2010 |
| N Lees Ltd | Professional & scientific | 2022 |
| Naneek Limited | Mining & quarrying | 2023 |
| NEG Plumbing and Heating Ltd | Construction | 2025 |
| Nellies Daycare Ballymena Limited | Health & social care | 2023 |
| Nellies Daycare Holding Company Limited | Financial services | 2023 |
| Nellies Daycare Magherafelt Limited | Health & social care | 2021 |
| Nellies Daycare Moneymore Limited | Health & social care | 2022 |
| Nellies Play Centre Ltd | Health & social care | 2026 |
| Neurotential Ltd | Professional & scientific | 2025 |
| Neville Bigger Contracts Limited | Construction | 2019 |
| New Dynasty BT45 Limited | Hospitality | 2025 |
| New Dynasty Zang Ltd | Hospitality | 2025 |
| New Jade House (N.I.) Ltd | Hospitality | 2023 |
| Newline Architects Ltd | Professional & scientific | 2012 |
| NGD Holdings Limited | Financial services | 2018 |
| NH1 Ltd | Health & social care | 2025 |
| NI Environmental Ltd | Agriculture & fishing | 2023 |
| NI Home Builders Limited | Other services | 2025 |
| NI K9 Ltd. | Administrative & support | 2013 |
| NI724546 Limited | Information & communication | 2024 |
| Nicolas Cars Ltd | Wholesale & retail | 2021 |
| Night Sky Holdings Ltd | Arts & recreation | 2025 |
| NL Contract Services Limited | Construction | 2022 |
| NME Skin & Beauty Ltd | Other services | 2025 |
| NMG & SON Ltd | Construction | 2005 |
| Noel Stewart Engineering Ltd | Professional & scientific | 2022 |
| Nomadic Works Ltd | Administrative & support | 2026 |
| North Power Ltd | Energy | 2011 |
| Northern Trees and Landscaping Ltd | Administrative & support | 2025 |
| Notorious Pizza Co. Ltd | Hospitality | 2022 |
| Notorious Wood Fired Co. Ltd | Hospitality | 2023 |
| NRG Nine Mile Hill Limited | Energy | 2015 |
| O & F Properties Ltd | Real estate | 2025 |
| O'Boyle Property Limited | Real estate | 2023 |
| O'Kane Holdings Ltd | Real estate | 1982 |
| O'Kane Supermarkets Limited | Real estate | 1982 |
| O'Kanes Investments Limited | Other services | 2018 |
| O'Kanes Limited | Wholesale & retail | 1999 |
| O'Kanes Trading Limited | Real estate | 2013 |
| O'Neill Consulting (N.I.) Ltd | Professional & scientific | 2019 |
| Oak Crescent Company Limited | Professional & scientific | 2015 |
| Oak Development Solutions (NI) Limited | Construction | 2020 |
| Oak Shelf Company Limited | Extraterritorial | 2017 |
| Oaklea Interiors Ltd | Manufacturing | 2018 |
| Oaklea Kitchens Ltd | Manufacturing | 2016 |
| Oakleaf Contracts (Europe) Ltd | Construction | 2001 |
| Oakleaf Contracts (North) Limited | Construction | 2021 |
| Oakleaf Contracts (South) Limited | Construction | 2025 |
| Oakleaf Contracts Limited | Construction | 2015 |
| Oakleaf Developments (N.I.) Holdings Limited | Financial services | 2018 |
| Oakleaf Developments (N.I.) Limited | Construction | 2015 |
| Oakleaf Europe (Holdings) Ltd | Financial services | 2018 |
| Oakleaf Homes (IRL) Limited | Real estate | 2006 |
| Oakleaf Mechanical Limited | Construction | 2020 |
| OHM Engineering Services Ltd | Construction | 2021 |
| OK Hospitality Limited | Hospitality | 2018 |