| Lowry Aero Ltd | Manufacturing | 2018 |
| LPJ Composites Limited | Manufacturing | 2025 |
| LRH Mechanical Ltd | Professional & scientific | 2024 |
| LT Aero Ltd | Manufacturing | 2025 |
| Lucky House 2026 Ltd | Hospitality | 2026 |
| Lucky House Carrickfergus Limited | Hospitality | 2023 |
| Lucy Lynn Limited | Wholesale & retail | 2014 |
| Lulu Projects Limited | Construction | 2025 |
| Lumivex Properties Ltd | Real estate | 2026 |
| Luna Nails & Spa Ltd | Other services | 2026 |
| LUQMAN2690 Ltd | Education | 2024 |
| Lusso TAN Online Ltd | Other services | 2024 |
| Lusso TAN Professional Ltd | Other services | 2023 |
| LV Auto Repair Ltd | Wholesale & retail | 2025 |
| LV Commercials Ltd | Manufacturing | 2023 |
| Lynx Electric Ltd | Construction | 2024 |
| Lúfar Global Consultants Ltd | Information & communication | 2021 |
| M J Kane & Co Accountants Ltd | Professional & scientific | 2007 |
| M Keers Engineering Limited | Manufacturing | 2010 |
| M&D Roofing Joinery Ltd | Construction | 2026 |
| Mack Consulting Engineering Ltd | Manufacturing | 2018 |
| Macroscopia Community Interest Company | Professional & scientific | 2015 |
| Mahoods Taxis N.I. Ltd | Transport & logistics | 2021 |
| Maintain Outdoor Services Ltd | Construction | 2023 |
| Malone Films Ltd | Information & communication | 2024 |
| Mama Chef Asian Cuisine Limited | Hospitality | 2023 |
| Mambo Restaurant Belfast Ltd | Hospitality | 2025 |
| Mano Aviation Services Ltd | Manufacturing | 2026 |
| Marapco Limited | Professional & scientific | 2007 |
| Marbel Property Development Ltd | Real estate | 2007 |
| Margaret Douglas Associates Limited | Administrative & support | 2020 |
| Margessa Ltd | Wholesale & retail | 2026 |
| Marindus Solutions (UK) Ltd | Manufacturing | 2024 |
| Marine Parade Whitehead Management Company Limited | Households | 2017 |
| Marine Sands Management Company Limited | Households | 2001 |
| Mark Allen Foundation Ltd | Other services | 2023 |
| Mark Cassells Limited | Administrative & support | 2020 |
| Mark Moore Tiling Ltd | Construction | 2022 |
| Marshall Property Management Ltd | Real estate | 2022 |
| Martin Park Apartments Services Limited | Households | 2007 |
| Mauds (1911) Ltd | Wholesale & retail | 2019 |
| Mauds (2302) Ltd | Wholesale & retail | 2023 |
| Mauds (Bangor) Ltd | Wholesale & retail | 2018 |
| Mauds (Holdings) Ltd | Financial services | 2018 |
| Mauds Ice Creams Ltd | Manufacturing | 2014 |
| MAX Go Limited | Education | 2019 |
| Mayur Indian Restaurant (Carrickfergus) Ltd | Hospitality | 2018 |
| Mayur Indian Restaurant Ltd | Hospitality | 2015 |
| Mayur Indian Takeaway Ltd | Hospitality | 2026 |
| Mayur Takeaway (Carrickfergus) Limited | Hospitality | 2018 |
| Mayur Takeaway Ltd | Hospitality | 2015 |
| Maywe Events Ltd | Other services | 2022 |
| MB Aerotech Ltd | Manufacturing | 2019 |
| MCA Developments (Antrim) Ltd | Construction | 2022 |
| Mcburney Property Limited | Real estate | 2026 |
| Mccune & Stewart Ltd | Manufacturing | 2019 |
| Mcdowell Consultancy Ltd | Health & social care | 2012 |
| MCG Accountancy Ltd | Professional & scientific | 2021 |
| Mcgregor Pharma Ltd | Wholesale & retail | 2026 |
| Mcilroy Cleaning Solutions Ltd | Administrative & support | 2018 |
| MCN Painting Contracts Ltd | Construction | 2021 |
| MCN Recritment Ltd | Administrative & support | 2025 |
| MDB Designs 2017 Ltd | Other services | 2017 |
| Merchant Festival Ltd | Wholesale & retail | 2025 |
| MET Contracts & Construction Ltd | Construction | 2025 |
| MG N.I. Ltd | Hospitality | 2026 |
| MGM Boats (U.K.) Ltd | Wholesale & retail | 2016 |
| Michael Tinsley Ltd | Information & communication | 2024 |
| Mike the Bookkeeper Ltd | Professional & scientific | 2022 |
| Milebush Management Limited | Households | 2004 |
| Millar Aerospace Ltd | Manufacturing | 2016 |
| Millars Courtyard Management Co Ltd | Extraterritorial | 2006 |
| Miller Property Specialist Limited | Real estate | 2022 |
| Minor Surgery NI Ltd | Health & social care | 2023 |
| Mirso Ltd | Manufacturing | 2017 |
| Mitchell Estates Ltd | Real estate | 1996 |
| MJ Kane Group Ltd | Administrative & support | 2023 |
| ML Aerospace Ltd | Manufacturing | 2017 |
| MMT Contracts Ltd | Construction | 2020 |
| MMT Tiling Contractor Ltd | Construction | 2022 |
| Mocon Limited | Real estate | 1985 |
| Model Professionals Ltd | Administrative & support | 2013 |
| Moghul Ltd | Hospitality | 2026 |
| MON SHA Allah Ltd | Transport & logistics | 2021 |
| Monroe Dwellings Ltd | Real estate | 2024 |
| Monroe Medical (NI) Limited | Health & social care | 2013 |
| Montana OIL and GAS Limited | Manufacturing | 2024 |
| Montgomery Chase Management Company Limited | Households | 2006 |
| Montgomery Meadows Management Company Limited | Households | 2020 |
| Motor Cycle Union of Ireland (Ulster Centre) Limited | Arts & recreation | 1981 |
| Mount Hill Management Services Ltd | Households | 2006 |
| MP Rentals Limited | Households | 2017 |
| MPF Engineering Ltd | Manufacturing | 2019 |
| Mr&Mrswwwonderful Limited | Hospitality | 2020 |
| MRL Entertainment Ltd | Other services | 2024 |
| Mrmaxcatch Ltd | Wholesale & retail | 2026 |
| Msotemac Ltd | Other services | 2022 |
| MTA Components Ltd | Administrative & support | 2006 |
| Mtan Consultancy Limited | Professional & scientific | 2024 |
| Multihub Limited | Information & communication | 2024 |