| M38 Ltd | Hospitality | 2019 |
| Mac-Lift Consultancy Ltd | Professional & scientific | 2021 |
| Mac’S Maintenance Ltd | Construction | 2026 |
| Madden Electrical Ltd | Construction | 2023 |
| MADE33 Ltd | Other services | 2026 |
| Maeve Ferguson Ltd | Professional & scientific | 2019 |
| Maffs Construction Ltd | Construction | 2016 |
| Magestic Ltd | Wholesale & retail | 2025 |
| Magherana Trustees Limited | Other services | 2013 |
| Magmel (Ballymena) Limited | Real estate | 2021 |
| Magnifeye Limited | Professional & scientific | 2021 |
| Maguire Energy Limited | Energy | 2013 |
| Maine Bakery Holdings Ltd | Financial services | 2023 |
| Maine Confectionery (Cullybackey) Limited | Real estate | 1981 |
| Maine Corporate Holdings Ltd | Financial services | 2025 |
| Maine House Galgorm Ltd | Hospitality | 2025 |
| Maine Mechanical Services Limited | Construction | 2020 |
| Maine Property & Lettings Management Ltd | Real estate | 2021 |
| Maineview Farm Limited | Agriculture & fishing | 2024 |
| Mainline Contracts Ltd | Construction | 2009 |
| Makovsky Vodka Company Limited | Extraterritorial | 1963 |
| MAL Electrical Contractors Limited | Construction | 2017 |
| Mallaboy Farm Ltd | Agriculture & fishing | 2024 |
| Mallaboy Finance Ltd | Financial services | 2023 |
| Mallaboy Property Ltd | Real estate | 2024 |
| Mallon Investments Ltd | Construction | 2023 |
| Malory Properties Limited | Real estate | 2010 |
| Manord Logistics Ltd | Transport & logistics | 2019 |
| Manz (2026) Ltd | Wholesale & retail | 2026 |
| MAP (N.I.) Ltd | Real estate | 2015 |
| MAP Real Estate Limited | Real estate | 2022 |
| MAR Networks Ltd | Energy | 2015 |
| Maration Limited | Real estate | 1997 |
| Marb Construction Projects Ltd | Construction | 2023 |
| Marcin & AGA Properties Ltd | Real estate | 2025 |
| Mark Devlin Productions Limited | Information & communication | 2026 |
| Marksman Industrial Company (NI) Limited | Wholesale & retail | 2015 |
| Marley Electrical Services Ltd | Construction | 2017 |
| Marrs Maintenance Services Ltd | Construction | 2012 |
| Marshadmayub Limited | Hospitality | 2026 |
| Martin Contracts (NI) Ltd | Construction | 2000 |
| Martin Engineering Supplies Limited | Wholesale & retail | 2005 |
| Martin Mcaleese Fruit & VEG Limited | Wholesale & retail | 2015 |
| Marx Corporate Limited | Wholesale & retail | 2019 |
| Matrix Animal Health Ltd | Manufacturing | 2019 |
| Mauds of Bushmills Ltd | Hospitality | 2024 |
| Maverick Fitness Limited | Arts & recreation | 2025 |
| MAW Architects Ltd | Professional & scientific | 2024 |
| MAX Investments NO.1 Limited | Financial services | 2016 |
| MAY Dawn Services Limited | Extraterritorial | 2012 |
| MB Motors Ballymena Ltd | Wholesale & retail | 2017 |
| MBD Holdings Limited | Financial services | 2025 |
| MBH Stores Ltd | Wholesale & retail | 2025 |
| MBJ Investments Limited | Real estate | 2014 |
| MC Custom Joinery Ltd | Manufacturing | 2012 |
| MC Flat Roofing Service Ltd | Construction | 2022 |
| Mcatamney Solicitors Limited | Professional & scientific | 2015 |
| MCC Computers Limited | Information & communication | 2002 |
| Mccarroll and SON Limited | Agriculture & fishing | 2015 |
| Mccarroll Plant Hire Limited | Administrative & support | 2015 |
| Mccartney & Crawford LLP | | 2012 |
| Mccartney Tiles NI Ltd | Wholesale & retail | 2011 |
| Mccaughan Marketing Ltd | Administrative & support | 2023 |
| Mccollam Marine Ltd. | Professional & scientific | 2011 |
| Mccollam Stone Ltd | Construction | 2008 |
| Mccormick Retail Limited | Wholesale & retail | 2026 |
| Mccosh Properties Limited | Real estate | 2004 |
| Mccurdy Fuels Limited | Wholesale & retail | 2017 |
| Mccurdy Holdings Limited | Financial services | 2025 |
| Mcdowell Property Services Limited | Professional & scientific | 2018 |
| Mcerlain Roof Cleaning Services Ltd | Construction | 2024 |
| Mcerlane Logistics Ltd | Transport & logistics | 2024 |
| Mcfarline Commerce Limited | Wholesale & retail | 2023 |
| MCG Services (NI) Limited | Professional & scientific | 2007 |
| Mcilhatton Properties Limited | Real estate | 2025 |
| Mcilroy Software Solutions Ltd | Professional & scientific | 2024 |
| MCK Wind Limited | Energy | 2014 |
| Mckay Electrical (NI) Ltd | Construction | 2018 |
| Mckay Enterprises Ltd | Wholesale & retail | 2025 |
| Mckeegan International Limited | Transport & logistics | 2003 |
| Mckendry Stoves Limited | Wholesale & retail | 2012 |
| Mckeown Software Engineering Ltd. | Information & communication | 2016 |
| Mckillop Retail Ltd | Wholesale & retail | 2013 |
| MCL Fabrications & Access Ltd | Construction | 2020 |
| Mcmullan Properties Limited | Real estate | 2020 |
| Mcmullan Transport Ltd | Transport & logistics | 2014 |
| Mcmullan's Central Bar Ltd | Hospitality | 2018 |
| MCR45 Limited | Wholesale & retail | 2023 |
| MCS Branding Limited | Wholesale & retail | 2022 |
| Mcshane Electrics Limited | Construction | 2015 |
| MD Racing Promotions Ltd | Arts & recreation | 2013 |
| MD Rally Prep Ltd | Arts & recreation | 2015 |
| MEA Affordable Food Club Limited | Manufacturing | 2022 |
| Medical AI Solutions Ltd | Health & social care | 2023 |
| Meganna Ltd | Hospitality | 2020 |
| Menopause Awareness NI CIC | Professional & scientific | 2023 |
| Mensa Holdings Ltd | Financial services | 2023 |
| Merville Inns (N.I.) Limited | Hospitality | 1974 |
| Meteor Software Limited | Information & communication | 2016 |
| Mezos Cafe Ltd | Hospitality | 2025 |