| MP Masonary Works Ltd | Construction | 2017 |
| MP Safety Ltd | Professional & scientific | 2016 |
| MP4 Holdings Limited | Financial services | 2017 |
| MP4 Property Ltd | Real estate | 2023 |
| MPD Construction Rostrevor Ltd | Construction | 2005 |
| MPF Contracts Ltd | Professional & scientific | 2015 |
| MPK II Consulting Limited | Construction | 2026 |
| MPK International Ltd | Professional & scientific | 2019 |
| MPM Freight Ltd | Transport & logistics | 2017 |
| MPM Performance Ltd | Wholesale & retail | 2024 |
| MPW N.I Limited | Hospitality | 2023 |
| MR Chris Collins | Health & social care | 2013 |
| MR Holdings (N.I.) Ltd | Financial services | 2020 |
| MR James Colville | Health & social care | 2012 |
| MR Raymond Moran | Health & social care | 2012 |
| MR Richard Hanson | Health & social care | 2012 |
| MR. Brian J.Mehigan | Health & social care | 2010 |
| MR. Colm Power | Health & social care | 2010 |
| MR. Conor Shields | Health & social care | 2011 |
| MR. Eadhbhard Mulligan | Health & social care | 2010 |
| MR. Eamon Beausang | Health & social care | 2010 |
| MR. Frank Kinsella | Health & social care | 2011 |
| MR. J'S Kitchen Ltd | Hospitality | 2024 |
| MR. Kiaran J. O'Malley | Health & social care | 2009 |
| MR. Malcolm Kell | Health & social care | 2011 |
| MR. Mark Rafferty | Health & social care | 2012 |
| MR. Michael Arthur Murphy | Health & social care | 2012 |
| MR. Mitchell Barry | Health & social care | 2014 |
| MR. Nasir Awan | Health & social care | 2012 |
| MR. Ralph Keane | Health & social care | 2010 |
| MRP Contracts Ltd | Construction | 2021 |
| MRP Holdings Limited | Financial services | 2022 |
| Mrpca Ltd | Extraterritorial | 2022 |
| MSG Construction Ltd | Construction | 2024 |
| MTA Technologies Ltd | Manufacturing | 2023 |
| MTB Cutz Ltd | Other services | 2024 |
| Muckna Ltd | Real estate | 2019 |
| Muff Ltd | Manufacturing | 2026 |
| Muiris Construction Limited | Construction | 2019 |
| Mulholland Transport Ltd | Transport & logistics | 2024 |
| Mulkerns Daisy Hill Ltd | Wholesale & retail | 2025 |
| Mulkerns Holdings Limited | Financial services | 2022 |
| Mullan Plant Hire Ltd | Construction | 2022 |
| Mulligan Motors Limited | Wholesale & retail | 2003 |
| Mulligan Transport Ltd | Transport & logistics | 2019 |
| Mullins & Doherty Construction Limited | Construction | 2021 |
| Mullion Consultancy Limited | Extraterritorial | 2021 |
| Mulray Investments Ltd | Real estate | 2026 |
| Multistar L.P. | | 2015 |
| Mulvaney Consultants Limited | Professional & scientific | 2015 |
| Mungo International Ltd | Wholesale & retail | 2022 |
| Murdock Builders Merchants Limited | Wholesale & retail | 2000 |
| Murdock Construction Limited | Construction | 1986 |
| Murdock Holdings Limited | Financial services | 2001 |
| Murland Utilities Ltd | Construction | 2023 |
| Murlough Sands Management Limited | Households | 2018 |
| Murnin's Autobody Ltd | Wholesale & retail | 2026 |
| Murnion Contracts Limited | Construction | 2015 |
| Murnion Plumbing & Heating Ltd | Construction | 2021 |
| Murphy Bros. (Farming) Limited | Agriculture & fishing | 1989 |
| Murphy Cattle NI Limited | Agriculture & fishing | 2025 |
| Murphy Chiropractic Ltd | Health & social care | 2014 |
| Murphy Contracts Ltd | Administrative & support | 2024 |
| Murphy Farming Limited | Agriculture & fishing | 1996 |
| Murphy Motor Sales Ltd | Wholesale & retail | 2015 |
| Murphy's Meigh Ltd | Hospitality | 2002 |
| Murphy's Roofing Ltd | Construction | 2018 |
| Murray & Mcevoy Limited | Construction | 2006 |
| Murray Funeral Services Ltd | Other services | 2019 |
| Murray Motorsport N.I Ltd | Wholesale & retail | 2016 |
| MW Electrical (NI) Ltd | Construction | 2011 |
| Mwac Holdings Ireland Ltd | Construction | 2017 |
| Mwac Property Ltd | Real estate | 2013 |
| MWT Logistics UK & Europe Ltd | Transport & logistics | 2025 |
| MX Estimating Limited | Professional & scientific | 2024 |
| My Garden of Music CIC | Arts & recreation | 2021 |
| My Little Uniform Ltd | Wholesale & retail | 2022 |
| My Mailbox Services Ltd | Other services | 2021 |
| MYB2020A Limited | Extraterritorial | 2020 |
| Myers Medical Limited | Health & social care | 2014 |
| Mylife Bathrooms Limited | Wholesale & retail | 2013 |
| Mynt Autocare Limited | Wholesale & retail | 2020 |
| Mystic Willow N. I. Ltd | Wholesale & retail | 2025 |
| N & R Contracts Limited | Construction | 2013 |
| N & T Developments Ltd | Construction | 1999 |
| N C Dental Clinic Ltd | Health & social care | 2012 |
| N DEV Consultancy NI Ltd | Professional & scientific | 2024 |
| N Donnelly Contracts Limited | Construction | 2026 |
| N Doyle Contracts Ltd | Construction | 2023 |
| N Fegan Plumbing & Heating Ltd | Construction | 2025 |
| N Mccann Contracts Ltd | Administrative & support | 2021 |
| N Shine Consultants Limited | Health & social care | 2011 |
| N W Kehoe & Sons Ltd | Wholesale & retail | 2019 |
| N.E.B Construction Ltd | Construction | 2021 |
| N.E.I Electrics Ltd | Administrative & support | 2017 |
| N.I.P. Pharma Limited | Wholesale & retail | 2005 |
| N5 Group Logistics & Shipping (IRL) Limited | Transport & logistics | 2023 |
| N8B Ltd | Wholesale & retail | 2023 |
| Nacelle Group Holdings Limited | Professional & scientific | 2015 |
| Nacelle Property Limited | Real estate | 2015 |