| Logan Construction & Facilities Management Ltd | Manufacturing | 2017 |
| Logwood Plant Centre Limited | Wholesale & retail | 2006 |
| Lolay Ltd | Wholesale & retail | 2023 |
| Loonburn Properties Limited | Real estate | 2020 |
| Loran Glen Property Management Ltd | Extraterritorial | 2008 |
| Loranville Land Management Ltd | Extraterritorial | 2006 |
| Lough Maintenance Limited | Extraterritorial | 2001 |
| Lough Shore Manor Management Company Ltd | Households | 2017 |
| Loughan Hall Management Co Ltd | Households | 2018 |
| Lowry & Sons Property Maintenance Ltd | Other services | 2021 |
| LPJ Logan Ltd | Administrative & support | 2017 |
| LT Couriers Ltd | Transport & logistics | 2017 |
| Lujed Ltd | Professional & scientific | 2025 |
| LVM Apartments Management Co Ltd | Households | 2022 |
| LVM Management Company Ltd | Households | 2019 |
| Lynden Gate Development Management Company Limited | Extraterritorial | 2006 |
| Lynne Taggart Ltd | Professional & scientific | 2017 |
| Lynview Mews Management Co. Ltd | Extraterritorial | 2004 |
| M&H Stewart Farms Ltd | Agriculture & fishing | 2020 |
| Magan Limited | Hospitality | 2026 |
| Maghery Management Company Ltd | Households | 2022 |
| Main Street Crumlin Management Company Ltd | Extraterritorial | 2008 |
| Main Street Vapour Limited | Wholesale & retail | 2016 |
| Malmar Automotive Ltd | Wholesale & retail | 2020 |
| Malone Place Management Co. Limited | Extraterritorial | 2005 |
| Maloon Crescent Management Co Ltd | Households | 2018 |
| Mamacita Media Ltd | Information & communication | 2022 |
| Manor Farm (Donaghadee) Management Ltd | Extraterritorial | 2005 |
| Manor Healthcare Limited | Health & social care | 2007 |
| Manse Manor Management Co Ltd | Households | 2018 |
| Mantle Property Developments Limited | Extraterritorial | 2016 |
| Mantle Stonemasonry Ltd | Construction | 2014 |
| Maple Villa Management Company Limited | Extraterritorial | 2007 |
| Maritime Quays Management Ltd | Households | 2018 |
| Martin Contracting Services Ltd | Construction | 2004 |
| Mason Consultancy Ltd | Information & communication | 2021 |
| Maverick Water Technologies Limited | Professional & scientific | 2025 |
| Mayfair Manco Limited | Households | 2024 |
| Mayfield Village Management Company Limited | Real estate | 2000 |
| MBL Innovations Ltd | Information & communication | 2026 |
| MBS Services Limited | Real estate | 2007 |
| MCA Vision Limited | Wholesale & retail | 2007 |
| Mccambridge Associates Limited | | 2003 |
| MCD Management Company Limited | Extraterritorial | 2002 |
| Mcfarland Cottages Limited | Hospitality | 2015 |
| Mcgladdery Estates Ltd | Real estate | 2025 |
| Mcgregor Commercials Ltd | Manufacturing | 2024 |
| MCK International Ltd | Wholesale & retail | 2007 |
| Mckinney GAS and OIL Ltd | Construction | 2021 |
| Mckinty Construction Limited | Manufacturing | 2019 |
| Mcmaster Residential Limited | Real estate | 2021 |
| Mcpv Ltd | Real estate | 2019 |
| Mdceng Ltd | Professional & scientific | 2024 |
| MDM Plumbing & GAS Limited | Construction | 2015 |
| MDR Financial Planning Ltd | Financial services | 2021 |
| Medgraphics Limited | Wholesale & retail | 1996 |
| Mediclean Hygiene Services Limited | Transport & logistics | 1988 |
| Medivent Services Limited | Professional & scientific | 2025 |
| Mervilla Ventures Limited | Professional & scientific | 2025 |
| Merville House Limited | Real estate | 2002 |
| MID Antrim Tractors | Wholesale & retail | 2021 |
| Midleton Hill Management Co Ltd | Households | 2023 |
| Mill Bridge (Hydepark) Management Company Limited | Households | 2020 |
| Mill Church Management Ltd | Extraterritorial | 2003 |
| Mill House Village Ltd | Extraterritorial | 2004 |
| Mill Pond Manor Property Management Ltd | Extraterritorial | 2008 |
| Millbank Events Company Ltd | Arts & recreation | 2001 |
| Millburn Mews Management Company Limited | Real estate | 2015 |
| Miller Motors Ltd | Extraterritorial | 2023 |
| Mills Homes Ltd | Construction | 2018 |
| Milltown Greens Company Ltd | Construction | 2021 |
| Millview Meadow Management Company Limited | Households | 2017 |
| Minana Ltd | Health & social care | 2025 |
| Mini Minds Play Cafe Ltd | Hospitality | 2025 |
| Mirrl Holdings (N.I.) Ltd | Real estate | 2016 |
| Mixin' With Christy’S Thermomix Ltd | Wholesale & retail | 2025 |
| MJM Marquees Ltd | Administrative & support | 2020 |
| Mksectbuildings Ltd | Manufacturing | 2026 |
| MNV Ltd. | Professional & scientific | 2010 |
| Moat Apartments Management Limited | Households | 2008 |
| Moira Gate MGT Co. Ltd | Households | 2020 |
| Moneymore Road Land Management Ltd | Extraterritorial | 2004 |
| Monkstown Management Company Limited | Households | 2005 |
| Montgomery Park Management Limited | Households | 2011 |
| Moor Road Land and Property Management Ltd | Households | 2016 |
| Motion Control Systems Ltd | Professional & scientific | 2016 |
| Mount Gilbert Management Co Ltd | Households | 2017 |
| Mountbatten Avenue Management Company Ltd | Households | 2009 |
| Move Independant Financial Services Limited | Financial services | 2006 |
| Move Right Therapy Ltd | Agriculture & fishing | 2017 |
| Moylinney Mill Management Ltd | Households | 2019 |
| MPF Media Ltd | Information & communication | 2019 |
| MRS Bubbles Ltd | Wholesale & retail | 2017 |
| Mulberry Lane Management Limited | Real estate | 2012 |
| Mullaghboy Mews Management Company Limited | Households | 2020 |
| MWJ Electrical Services Ltd | Construction | 2024 |
| N I Trade Sales Ltd | Wholesale & retail | 2009 |
| N.J. Nelson Group Ltd | Financial services | 2021 |
| Namastay India Ltd | Hospitality | 2020 |
| Namastay INDIA1 Limited | Hospitality | 2022 |