| MG Construction & Development Ltd | Construction | 2014 |
| MG Implants & Facial Aesthetics Ltd | Health & social care | 2021 |
| Michael Galloway Construction Limited | Construction | 2011 |
| MID Down Integrated College Ltd | Education | 2025 |
| Midnight Property Group Ltd | Construction | 2023 |
| Miga Contracts Limited | Construction | 2025 |
| Milestone Sprayers Ltd | Wholesale & retail | 2017 |
| Milligan Auto Sales Limited | Wholesale & retail | 2018 |
| Mind Revitalise Ltd | Professional & scientific | 2020 |
| Mjbd Limited | Wholesale & retail | 2022 |
| MJK Plumbing Services Ltd | Construction | 2013 |
| MK Joinery Limited | Construction | 2015 |
| ML Talent Solutions Ltd | Administrative & support | 2026 |
| MLR Recruiting Ltd | Administrative & support | 2018 |
| MMC Painting Ltd | Construction | 2026 |
| MMC Plant Hire & Groundworks Ltd | Construction | 2025 |
| Mmcgarrity Painting Ltd | Construction | 2026 |
| Modern Wine Company Ltd | Wholesale & retail | 2023 |
| Mollan Medical Ltd | Administrative & support | 2010 |
| Moneycarragh Management Company Limited | Households | 2001 |
| MOP Mechanical Limited | Construction | 2025 |
| More Than Floors Limited | Construction | 2016 |
| Morgan & Brown Ltd | Construction | 2023 |
| Morgan Young Consulting Limited | Professional & scientific | 2016 |
| Morrissey CA Limited | Professional & scientific | 2015 |
| Moss Hill Contracts Ltd | Construction | 2026 |
| Mountpanther Farm Park Ltd | Arts & recreation | 2017 |
| Mourne Access Solutions Limited | Construction | 2019 |
| Mourne and Down Property Services Ltd | Construction | 2026 |
| Mourne View Apartments (Downpatrick) Limited | Real estate | 1987 |
| Mourne View Limited | Administrative & support | 2022 |
| MPE 2018 Ltd | Arts & recreation | 2018 |
| MPM Light Commercials Ltd | Wholesale & retail | 2026 |
| MR Smyth Ltd | Professional & scientific | 2016 |
| MRM Fast Food Limited | Hospitality | 2024 |
| Mstw Aviation Consulting Limited | Professional & scientific | 2026 |
| Muldell Ltd | Professional & scientific | 2018 |
| Mullans Ltd | Hospitality | 2011 |
| Mwac Holdings Ltd | Other services | 2019 |
| My Body Pilates Ltd | Arts & recreation | 2025 |
| N N E (Properties & Developments) Ltd | Real estate | 2011 |
| N. Fowler Electrical Ltd | Construction | 2025 |
| Naghan Limited | Agriculture & fishing | 2004 |
| Naghan Properties Ltd | Real estate | 2018 |
| Natural Hair Company Limited | Other services | 2002 |
| NBA Groundworks Ltd | Construction | 2024 |
| Neil Carnegie Consultancy Ltd | Professional & scientific | 2021 |
| NEO Safety Ltd | Professional & scientific | 2026 |
| Newbridge Plumbing & Heating Services Ltd | Construction | 2023 |
| Nexora Design Ltd | Wholesale & retail | 2026 |
| NI Golf Tours Ltd | Administrative & support | 2012 |
| NI Refurbs Ltd | Construction | 2021 |
| NI Restoration Services Ltd | Wholesale & retail | 2021 |
| NI Skin Medic Ltd | Health & social care | 2021 |
| NI Speaks OUT | Education | 2011 |
| Norglen Ltd | Real estate | 2023 |
| Norman Elliott Accountants Limited | Professional & scientific | 2021 |
| North Ambition Ltd | Wholesale & retail | 2024 |
| Northern Leisure (NI) Ltd | Arts & recreation | 2013 |
| Northern Luthiers Collective Ltd | Administrative & support | 2024 |
| NOT Just Neon Ltd | Wholesale & retail | 2024 |
| Novell Property and Gardens Ltd | Construction | 2023 |
| NPO Stationers Limited | Wholesale & retail | 2009 |
| NR1 Trade Ltd | Wholesale & retail | 2021 |
| Nugroupni Ltd | Construction | 2021 |
| O'Kane Resourcing Ltd | Administrative & support | 2014 |
| O'Toole Wealth Management Ltd. | Financial services | 2026 |
| Oakley Renewables Limited | Energy | 2013 |
| OK Electrical Engineering Services Ltd | Professional & scientific | 2025 |
| OK Fabrications & Welding Limited | Manufacturing | 2022 |
| Old Commercial Bar Limited | Hospitality | 2018 |
| Old GUY Films Ltd | Information & communication | 2022 |
| Ollard Westcombe (2000) Limited | Manufacturing | 1999 |
| Olympus Engagements Ltd | Wholesale & retail | 2020 |
| Olympus Gym Co.Down Ltd | Arts & recreation | 2025 |
| Opinionatedgeek Ltd | Information & communication | 1998 |
| Ordantum Limited | Information & communication | 2008 |
| OYG Ltd | Wholesale & retail | 2025 |
| P & M Beer and Spirits Ltd | Hospitality | 2025 |
| P & U Ward Building Services Ltd | Construction | 2019 |
| P L Polly Racing Limited | Agriculture & fishing | 2020 |
| P Turley Ltd | Arts & recreation | 2017 |
| P Ward Car & Commercials Ltd | Wholesale & retail | 2024 |
| P&G Bricklaying Limited | Construction | 2016 |
| P.C.M. Developments Ltd | Construction | 2005 |
| P.M. Construction (N.I.) Limited | Construction | 2018 |
| P.O.S Electrical Supplies Limited | Wholesale & retail | 2016 |
| PA Contracts Ltd | Construction | 2025 |
| Padani 62 Ltd | Wholesale & retail | 2018 |
| Parent Action C.I.C. | Education | 2017 |
| Parful Golf Ltd | Wholesale & retail | 2025 |
| Pat's Printers NI Limited | Manufacturing | 2019 |
| Pathway Theatre Productions Ltd | Arts & recreation | 2026 |
| PBC Conservation Limited | Mining & quarrying | 2020 |
| Pedellex Ltd | Wholesale & retail | 2023 |
| Peking Chen Limited | Hospitality | 2019 |
| Pence Holdings Limited | Real estate | 2026 |
| Perfected Media Ltd | Professional & scientific | 2025 |
| Peter Turley Properties Ltd | Real estate | 2025 |
| Phillips Contracts (DPK) Ltd | Construction | 2011 |