| Mcintire Partners LLP | | 2020 |
| Mckinlay & Co (Derry), Limited | Real estate | 1940 |
| Mckinley Property Group Ltd | Real estate | 2025 |
| MCL Services (NI) Ltd. | Information & communication | 2014 |
| Mclaughl Limited | Wholesale & retail | 2025 |
| Mclaughlin Trading Ltd | Hospitality | 2025 |
| MCM Drylining Limited | Construction | 2024 |
| MCM Partitions Ltd | Construction | 2020 |
| MCN Contracts NI Limited | Construction | 2016 |
| MCN Metal Partitions Ltd | Construction | 2016 |
| Mcnamee Construction Ltd | Construction | 2018 |
| Mcor Drylining Ltd | Construction | 2025 |
| Mcrossan Limited | Information & communication | 2021 |
| MCS Contracts Limited | Construction | 2015 |
| MCS Enterprises Limited | Health & social care | 2019 |
| Mcshane Engineering Ltd | Professional & scientific | 2025 |
| MD Consulting NW Ltd | Construction | 2022 |
| MD Shah Medical Ltd | Other services | 2015 |
| Meadow Properties & Investments Limited | Real estate | 2025 |
| Meadowbank Limited | Professional & scientific | 1993 |
| MEC Sizzles Ltd | Hospitality | 2023 |
| Mechanical Installations & Maintenance (N.I.) Limited | Manufacturing | 1994 |
| Mechanical Recruitment Solutions Ltd | Administrative & support | 2019 |
| Mediastrong CIC | Health & social care | 2024 |
| Mediastrong Group Ltd | Education | 2025 |
| Medical Outcome Limited | Professional & scientific | 2013 |
| Medina Supermarket Derry Limited | Wholesale & retail | 2025 |
| Megan Macedo Limited | Information & communication | 2013 |
| MEH Investments Limited | Real estate | 2017 |
| Mellova Investments | Financial services | 2026 |
| Mellova Property | Real estate | 2026 |
| Memberassistant Ltd | Information & communication | 2025 |
| Mena's Events Catering Ltd | Hospitality | 2026 |
| Mena's Pizzeria and Coffee House Ltd | Hospitality | 2026 |
| Mena’S Woodfired Pizzas Ltd | Hospitality | 2025 |
| Merar Ltd | Real estate | 2021 |
| Merchants Bay Limited | Construction | 2022 |
| Merritt Contracts Limited | Construction | 2017 |
| Metacompliance Limited | Information & communication | 2003 |
| Metadeck Ltd | Information & communication | 2015 |
| Metal Stud Ltd. | Manufacturing | 2016 |
| MF & M Property Ltd | Real estate | 2021 |
| Mfsportactive Limited | Administrative & support | 2020 |
| Mgfamco Ltd | Administrative & support | 2017 |
| MGN Enterprises Ltd | Hospitality | 2015 |
| Miana Construction Ltd | Construction | 1997 |
| Micaela Greenwood Associates Ltd | Health & social care | 2020 |
| Michael Deery Ltd | Construction | 2018 |
| Michael Doherty Construction & Associates Limited | Construction | 1995 |
| Michael O'Hara Maintenance Contracts Limited | Construction | 2012 |
| Michi Limited | Wholesale & retail | 2025 |
| Microfy Limited | Professional & scientific | 2025 |
| Midas Steel Ltd | Construction | 2020 |
| Middlesex Property Investments & Services Ltd | Real estate | 2021 |
| MIKURO8 Ltd | Wholesale & retail | 2023 |
| Mill Wright Products Limited | Wholesale & retail | 2004 |
| Million Dollar Fitness Limited | Education | 2013 |
| Milltek Interior Fit-Outs Ltd | Construction | 2017 |
| Milltown Securities Ltd | Administrative & support | 2019 |
| Millwell Properties Limited | Real estate | 2012 |
| Mind-Mapper Ltd | Information & communication | 2020 |
| Mindflow Limited | Professional & scientific | 2026 |
| Mindset & Performance Ltd | Professional & scientific | 2019 |
| Mirtna Management Ltd | Financial services | 2012 |
| Mission Hall Quilts Limited | Transport & logistics | 2006 |
| Mister C Culmore Limited | Hospitality | 2021 |
| Mitch Davis Ltd | Information & communication | 2022 |
| MJ Bradley Ltd | Manufacturing | 2022 |
| Mj's Menswear Ltd | Wholesale & retail | 2021 |
| MJF Enterprises Limited | Wholesale & retail | 2025 |
| Mjfplant and Machinery Ltd | Construction | 2026 |
| MJM Contracting Ltd | Professional & scientific | 2019 |
| Mjscorporatedebtsolutions Limited | Administrative & support | 2025 |
| Mjsdebtagencyandcollection Limited | Administrative & support | 2025 |
| MK 5 Ltd | Real estate | 2019 |
| MK Bhavsar Ltd | Health & social care | 2012 |
| MK Online Coaching Ltd | Arts & recreation | 2022 |
| MKA Planning Limited | Professional & scientific | 2003 |
| MKM Enterprises Limited | Hospitality | 2017 |
| ML Marine Services Ltd | Professional & scientific | 2022 |
| ML Property Management Ltd | Real estate | 2020 |
| Mltc Ltd | Real estate | 2025 |
| MMA (Derry) Electrical Ltd | Construction | 2016 |
| Mmbo Ltd | Wholesale & retail | 2025 |
| Mmbp Recruitment Ltd | Health & social care | 2024 |
| MMC Associates Limited | Construction | 2016 |
| MMC Bars Limited | Hospitality | 2014 |
| Mmcl Enterprises Limited | Arts & recreation | 2019 |
| Mmcn Ecom Limited | Wholesale & retail | 2024 |
| MMG Developments Ireland Ltd | Construction | 2019 |
| MMG Electric Limited | Construction | 2024 |
| MMS Groundworks Limited | Construction | 2026 |
| MMS Utilities Limited | Administrative & support | 2019 |
| MO Property Lettings Ltd | Households | 2023 |
| Mobile Medic Derry Limited | Wholesale & retail | 2024 |
| MOD Mechanical Ltd | Professional & scientific | 2025 |
| MOD Properties Limited | Real estate | 2008 |
| MOD Toys and Entertainment Limited | Wholesale & retail | 2019 |
| Mode Work and School Ltd | Wholesale & retail | 2023 |
| Modern Advantage Ltd | Real estate | 2026 |