| Millar Estates (Beechill House) NI Ltd | Real estate | 2015 |
| Millar Fabrication and Sons Holdings Limited | Financial services | 2022 |
| Millar Plant Sales Ltd | Wholesale & retail | 2008 |
| Millburn Community Development Ltd | Health & social care | 2023 |
| Millburn Community Preschool Playgroup Limited | Education | 2011 |
| Millfields Crescent Management Company Ltd | Households | 2003 |
| Millfields Management Company Limited | Households | 2002 |
| Millfort Drive Management Company Limited | Households | 2020 |
| Millmac Sales Ltd | Wholesale & retail | 2013 |
| Millrush Drive Management Company Ltd | Construction | 2009 |
| Misfit Hobbies Ltd | Manufacturing | 2025 |
| Misfit Hobbies Retail Ltd | Wholesale & retail | 2025 |
| Missalium Press Ltd | Information & communication | 2024 |
| Mister WU Limited | Hospitality | 2024 |
| MIU MIU Nails & Spa Limited | Other services | 2024 |
| MKB Co NO 10 Limited | Hospitality | 2005 |
| MKM Enterprises (2023) Ltd | Hospitality | 2023 |
| MKP Accountants Ltd | Professional & scientific | 2025 |
| ML Connect (N. Ireland) Ltd | Wholesale & retail | 2021 |
| MM Agri Ltd | Agriculture & fishing | 2024 |
| MMW Fit-Out Limited | Construction | 2012 |
| Model Floors Ltd | Construction | 2016 |
| Modern Surfacing Ltd | Construction | 2023 |
| Moneygran Holdings Limited | Financial services | 2025 |
| Montgomery Close Management Association Limited | Real estate | 2001 |
| Montgomery Irwin Architects Ltd | Professional & scientific | 2008 |
| Moore (N.I.) LLP | | 2013 |
| Morelli Gelateria Ltd | Manufacturing | 2015 |
| Morelli Ice Cream Ltd | Manufacturing | 2014 |
| Morrliving Limited | Other services | 2024 |
| Mortgage/Property Sales & Rentals Ltd | Real estate | 2012 |
| Motoplus Motorcycles Ltd | Wholesale & retail | 2014 |
| Motte Farm Management Company Limited | Households | 2003 |
| Moylagh Meadows Management Limited | Households | 2017 |
| MRP Property Management Ltd | Real estate | 2024 |
| MRP Rope Access Ltd. | Construction | 2017 |
| MS Decorating Limited | Construction | 2010 |
| MSB Enterprises (NI) Limited | Hospitality | 2016 |
| Mudanjiang Ltd | Health & social care | 2012 |
| Mulberry Bush (NI) Ltd - the | Professional & scientific | 2005 |
| Mulco Group Ltd | Wholesale & retail | 2017 |
| Mullan Consulting Engineers Ltd. | Professional & scientific | 2011 |
| Mullan Contracts (2016) Ltd | Construction | 2016 |
| Mullan Contracts (2020) Ltd | Construction | 2020 |
| Mullan Energy Ltd | Energy | 2015 |
| Mullan Farms Ltd | Agriculture & fishing | 2026 |
| Mullan Group Ltd | Financial services | 2022 |
| Mullan Holdings (Liverpool) Ltd | Wholesale & retail | 2024 |
| Munro Executives Ltd | Construction | 2015 |
| Music Tutors' Services Ltd | Education | 2019 |
| Mussenden Management Company Limited | Households | 2008 |
| My Lash Limited | Other services | 2024 |
| Myhealthclinicni Ltd | Health & social care | 2025 |
| Mystee Ltd | Administrative & support | 2022 |
| N White Construction Ltd | Construction | 2016 |
| N.I. Networks Limited | Construction | 2014 |
| NB Autoparts Ltd | Wholesale & retail | 2024 |
| NB Homes Limited | Construction | 2016 |
| NBB Shopfitting Ltd | Construction | 2006 |
| NBG Holdings Limited | Financial services | 2024 |
| Neivki Limited | Professional & scientific | 2025 |
| Nevco (NI) Limited | Financial services | 2005 |
| Nevin Properties Limited | Real estate | 2014 |
| New Golden House Kilrea Limited | Hospitality | 2023 |
| New View Contracts Limited | Construction | 2021 |
| Newbridge Restaurants Limited | Extraterritorial | 2014 |
| Next Step First AID Solutions Ltd | Other services | 2020 |
| NI Developments Ltd | Construction | 2018 |
| Nicholl International Transport Ltd | Transport & logistics | 2025 |
| NII Clean Limited | Administrative & support | 2021 |
| Nitec Auto Repairs Ltd | Wholesale & retail | 2022 |
| Nmam Restaurants Ltd | Hospitality | 2024 |
| Nonglak Mcfadden Ltd | Manufacturing | 2008 |
| Noord Outdoor Ltd | Wholesale & retail | 2026 |
| Norris Bros Services Ltd | Other services | 2026 |
| Norris Brothers Farms Limited | Agriculture & fishing | 2022 |
| North Coast (N.I.) Limited | Wholesale & retail | 2023 |
| North Coast Business Consultancy Ltd | Professional & scientific | 2026 |
| North Coast Capital Ltd | Real estate | 2018 |
| North Coast Cleaning Ltd | Administrative & support | 2024 |
| North Coast Community Transport | Transport & logistics | 2000 |
| North Coast Community Wellbeing CIC | Health & social care | 2025 |
| North Coast Customs Group Ltd | Wholesale & retail | 2025 |
| North Coast Facility Services Ltd | Hospitality | 2026 |
| North Coast Financial Ltd | Financial services | 2024 |
| North Coast Golf Sims Ltd | Administrative & support | 2026 |
| North Coast Logistics Ltd | Transport & logistics | 2022 |
| North Coast Pilates & Physiotherapy Limited | Health & social care | 2019 |
| North Coast Wind Limited | Energy | 2015 |
| Northbrook Commercials Limited | Transport & logistics | 2020 |
| Northern Ireland International Youth Football CUP Limited | Arts & recreation | 1998 |
| Northern Real Estate Ltd | Real estate | 2008 |
| Northern Road Markings Limited | Construction | 1984 |
| Northwest Fuels Ltd | Wholesale & retail | 2012 |
| Novara Health Ltd | Health & social care | 2025 |
| Nq&S Autocare Ltd | Wholesale & retail | 2026 |
| NT Agri Ltd | Manufacturing | 2021 |
| Nudge App Ltd | Information & communication | 2025 |
| Nutt Promotions and Travel Limited | Administrative & support | 2014 |
| Nutt Property Investments Limited | Administrative & support | 2025 |