| Mcgonagle Innovations Ltd | Manufacturing | 2023 |
| MCI (Derry) Limited | Financial services | 2023 |
| MCI Strategic Solutions Limited | Professional & scientific | 2023 |
| Mcivor GAS Services Ltd | Construction | 2005 |
| MCK Utilities Limited | Construction | 2020 |
| Mckinney Plant & Safety Ltd | Construction | 2004 |
| MCL Hospitality Management Ltd | Professional & scientific | 2023 |
| Mclaughlin and Co Limited | Professional & scientific | 2015 |
| Mclaughlin Funeral Directors Limited | Other services | 2015 |
| Mclaughlin Taylor Drylining Limited | Construction | 2009 |
| Mcmaster Properties Limited | Real estate | 1985 |
| Mcnamee Construction Services Ltd | Construction | 2014 |
| Mcphilemy Ventures NI Ltd | Administrative & support | 2024 |
| MD Inspection Services & Supplies Ltd | Administrative & support | 2022 |
| MD Motor Repairs Limited | Wholesale & retail | 2024 |
| MDE Electrical Solutions Limited | Professional & scientific | 2022 |
| MDT Bricklaying Limited | Construction | 2020 |
| Meenan Square Developments Ltd | Real estate | 2023 |
| Mellon Properties Limited | Households | 2006 |
| Merlan Properties Limited | Extraterritorial | 2007 |
| Merrion Projects Ltd | Transport & logistics | 2021 |
| Mersey Red Properties Ltd | Real estate | 2025 |
| Metaverse MOD Squad UK Ltd | Administrative & support | 2014 |
| MFC Sports Limited | Wholesale & retail | 2016 |
| Mfhco Ltd | Financial services | 2024 |
| MFS Lots Ltd | Construction | 2021 |
| MG Natural Resources Limited | Agriculture & fishing | 2016 |
| Michael Deery Hair & Co Limited | Other services | 2025 |
| Michael Donaghy (Painting & Decorating Contractor) Limited | Construction | 2000 |
| Michael Mclaughlin & Sons Limited | Wholesale & retail | 1978 |
| Michele Jones Ltd | Other services | 2011 |
| Midas Letting Agents Limited | Real estate | 2010 |
| Midas Properties (Ireland) Limited | Real estate | 2014 |
| Mill Path Manufacturing Solutions Ltd | Professional & scientific | 2020 |
| Millennium Forum Productions Ltd | Arts & recreation | 2016 |
| Millennium Three Solutions Ltd | | 1996 |
| Millpro Company Ltd | Wholesale & retail | 2022 |
| Milltown Legal Consulting Limited | Professional & scientific | 2020 |
| Mind Technica Ltd | Wholesale & retail | 2023 |
| Misneach Ltd | Health & social care | 2026 |
| MJ Farms Ltd | Agriculture & fishing | 2006 |
| Mjjohn Ltd | Hospitality | 2019 |
| MK Electrical (N.I) Ltd | Construction | 2019 |
| ML Anaesthetics Limited | Health & social care | 2026 |
| MLS Homes Ltd | Construction | 2018 |
| MMC Castles Ltd | Arts & recreation | 2026 |
| MMC Parties Ltd | Arts & recreation | 2026 |
| MMN Electrical Ltd | Construction | 2019 |
| MO Brabus Limited | Other services | 2015 |
| Molloy's Fish Ltd | Wholesale & retail | 2021 |
| Molly Malone Tours Ltd | Administrative & support | 2024 |
| Moneymore Properties Ltd | Administrative & support | 2017 |
| Moorcon Developments Limited | Construction | 2014 |
| Moorcon Limited | Construction | 2006 |
| Moore Safety Consultant Ltd | Professional & scientific | 2022 |
| MOR Services Limited | Construction | 2019 |
| Morivita Ltd | Other services | 2026 |
| Mosetta Nominees | Financial services | 2013 |
| Mota Urban Mobility Solutions Ltd | Manufacturing | 2024 |
| Motoworld LK Limited | Wholesale & retail | 2025 |
| Mouldings Direct Derry Limited | Construction | 2020 |
| Mountaintop Carpets (Holdings) Ltd | Financial services | 2024 |
| Mountsandel Developments Limited | Construction | 2024 |
| MPR Berryhill Ltd | Wholesale & retail | 2023 |
| MPS Confectionary Limited | Wholesale & retail | 2022 |
| MSK Autos Ltd | Wholesale & retail | 2025 |
| MSK Bhavsar Limited | Real estate | 2023 |
| MTH Sales Ltd | Wholesale & retail | 2020 |
| Mtrac Assets Ltd | Real estate | 2025 |
| Muldonagh Contracts Ltd | Construction | 2017 |
| Mulhall Contracts NI Limited | Professional & scientific | 2017 |
| Mullan Auto Repairs Ltd | Wholesale & retail | 2022 |
| Mullarkey Pedersen Architects Ltd | Professional & scientific | 2023 |
| Multishower GB Ltd | Wholesale & retail | 2008 |
| Museum of Free Derry Ltd | Arts & recreation | 2015 |
| Music Capital Limited | Arts & recreation | 2021 |
| Music KIN C.I.C. | Education | 2021 |
| MVS (24) Ltd | Hospitality | 2024 |
| My Family Matters Foundation Ltd | Other services | 2023 |
| My Tracks IE Ltd | Wholesale & retail | 2024 |
| N. Mcloone & Co. Ltd | Wholesale & retail | 1993 |
| Nailor's ROW Properties Ltd | Real estate | 2021 |
| NEC Aspire Technology Systems Limited | Information & communication | 2020 |
| Neighbourhood Management Team Limited | Other services | 1996 |
| Nelson Ecological Consulting Ltd | Professional & scientific | 2026 |
| Nerve Digital Ltd. | Education | 2015 |
| Neuroconcise Ltd. | Manufacturing | 2016 |
| Newspread Ltd | | 2008 |
| Newtoun Inn Limited | Hospitality | 1980 |
| Newtownstewart Contracts Limited | Construction | 2010 |
| NI Fleet Limited | Construction | 2015 |
| NI School of Massage Ltd | Education | 2018 |
| Nicor Facilities Management (FM) Ltd | Professional & scientific | 2014 |
| Night Dial Ltd | Information & communication | 2023 |
| Nine Lives Coffee Limited | Hospitality | 2026 |
| NL1 Investments Ltd | Real estate | 2024 |
| Nlspgc Ltd | Wholesale & retail | 2024 |
| NMM Designs Ltd | Professional & scientific | 2022 |
| NON Joinery Limited | Construction | 2018 |
| Non-Carbon Energy Limited | Professional & scientific | 2017 |