| MEL Agri Hire Ltd | Administrative & support | 2024 |
| Melia Boutique Ltd | Wholesale & retail | 2018 |
| Merall Contracts Limited | Construction | 2014 |
| Meridian One Ltd | Professional & scientific | 2025 |
| Metro Medical Services Ltd | Health & social care | 2024 |
| MFS Fuel Services Ltd | Wholesale & retail | 2011 |
| MG Accountants (Portadown) | Professional & scientific | 2014 |
| MG Formula Ltd | Wholesale & retail | 2021 |
| Mhaca Holdings | Financial services | 2016 |
| MHT Ireland Ltd | Transport & logistics | 2012 |
| Miamo Limited | Wholesale & retail | 2025 |
| Michael Mcginn Mechanical Ltd | Construction | 2010 |
| Michael Rafferty Logistics Ltd | Transport & logistics | 2016 |
| Mick's Tractor Hire Limited | Administrative & support | 2017 |
| Midroe Ltd | Construction | 2026 |
| Mighte Limited | Other services | 2019 |
| Milestone Planning Solutions Ltd | Construction | 2025 |
| Milestone Way Holdings Ltd | Construction | 2022 |
| Milford Biogas Limited | Energy | 2017 |
| Milford Cattle Ltd | Agriculture & fishing | 2023 |
| Milford Developments Ltd | Construction | 2013 |
| Milford Manjjw Project Ltd | Construction | 2024 |
| Millrow Enterprises Limited | Construction | 2003 |
| Mills International Trading Ltd | Wholesale & retail | 2024 |
| Mills Property Ireland Ltd | Real estate | 2024 |
| Millview Fuels Freight Ltd | Wholesale & retail | 2008 |
| Millview Residential Properties Limited | Real estate | 2018 |
| Millview Windows Limited | Construction | 2016 |
| Mind Your Self - Aire Dhuit Ltd | Health & social care | 2026 |
| Minority Ethnic Support Armagh CIC | Other services | 2026 |
| Minority Ethnic Support Ltd | Information & communication | 2026 |
| Mister Deery & Co Ltd | Professional & scientific | 2018 |
| Mitchell Motors Limited | Wholesale & retail | 2025 |
| Mitko Bulgaria Barber Limited | Other services | 2025 |
| Mjlt Limited | Transport & logistics | 2021 |
| MKE (N.I.) Limited | Energy | 2015 |
| ML Contracts (Keady) Ltd | Construction | 2023 |
| MMK1 Trading Ltd | Wholesale & retail | 2025 |
| MMR Armagh Ltd | Wholesale & retail | 2021 |
| MN Electrics (Armagh) Ltd | Construction | 2018 |
| Mobility Direct Ireland Ltd | Wholesale & retail | 2019 |
| Modified Bitumen Membrane Ltd | Wholesale & retail | 2019 |
| Modulin Limited | Wholesale & retail | 2020 |
| Moffett Belfast CP Unlimited | Real estate | 2018 |
| Moira Management Limited | Households | 1997 |
| Molloy Metals (L) Ltd | Water & waste | 2018 |
| Molly Road Unlimited | Energy | 2013 |
| Momentum Construction Planning Ltd | Professional & scientific | 2022 |
| Mone Funeral Directors Ltd | Other services | 2026 |
| Monitcom Limited | | 2000 |
| Montevista Properties Limited | Real estate | 2014 |
| Mooney Matthews (Armagh) Ltd | Professional & scientific | 2013 |
| MOR Garage Doors Ltd | Construction | 2015 |
| Morgan Transport Consultancy Limited | Transport & logistics | 2017 |
| Morton Bulk Transport Limited | Transport & logistics | 2013 |
| Moss Construction (NI) Limited | Construction | 1998 |
| Moss Trans Limited | Transport & logistics | 2025 |
| Motomerchants Limited | Wholesale & retail | 2015 |
| Motor Electric (Armagh) Limited | Wholesale & retail | 1975 |
| Mount White Contracts Limited | Construction | 2021 |
| Mount White Properties Limited | Real estate | 2022 |
| Mountnorris General Supplies Limited | Wholesale & retail | 2020 |
| Mourne Developments Ltd | Professional & scientific | 2007 |
| Mourneview Investments Ltd | Real estate | 2023 |
| Moyallen Developments Limited | Construction | 2007 |
| Moyallen Holdings Limited | Professional & scientific | 2007 |
| Moyraverty Capital Limited | Financial services | 2023 |
| Moyraverty Investments Limited | Real estate | 2022 |
| MPK Roofing Limited | Construction | 2018 |
| MR Foods Wholesale Ltd | Hospitality | 2013 |
| MR Haulage Ltd | Transport & logistics | 2013 |
| MR J & MRS S Mcdonnell Ltd | Real estate | 2026 |
| MSC Foyleside Ltd | Real estate | 2024 |
| MSC FW Ltd | Real estate | 2025 |
| MSC Ovolo Ltd | Hospitality | 1987 |
| MSC RE Ltd | Real estate | 2021 |
| MSC Rushmere Ltd | Financial services | 2022 |
| MSC Yeovil Ltd | Real estate | 2022 |
| MT Mckeown Taxi & BUS Hire Limited | Transport & logistics | 2022 |
| MTC Estates Limited | Real estate | 2020 |
| Mtes (N.I.) Ltd | Construction | 2026 |
| MTM Engineering (UK) Limited | Construction | 2023 |
| Muldoon Flat Roofing Ltd | Construction | 2026 |
| Mullabrack Parish Hall Limited | Other services | 2011 |
| Mullan's Killylea Road Limited | Wholesale & retail | 2018 |
| Mullan's Markethill Limited | Wholesale & retail | 2018 |
| Muntermellan Ltd | Real estate | 2025 |
| Murphy Investments Group Ltd | Financial services | 2026 |
| Murphy Surveys Ltd | Construction | 2025 |
| Murphy's Tiles & Bathrooms Ltd. | Wholesale & retail | 2023 |
| Murphygmc Limited | Construction | 2017 |
| Murray Excel (Stock Trading) Ltd | Wholesale & retail | 2016 |
| Murray Haulage Limited | Transport & logistics | 2014 |
| My Thai Armagh Ltd | Hospitality | 2026 |
| Mybids.Co.Uk Ltd | Wholesale & retail | 2025 |
| Mythic Digital Marketing Ltd | Professional & scientific | 2023 |
| N Finlay Refrigeration Ltd | Construction | 2023 |
| N Mckernan Ltd | Construction | 2019 |
| N&H Trade Ltd | Wholesale & retail | 2025 |
| N&P Commercial Refurbishment Limited | Transport & logistics | 2020 |