| Mourne Motorcycle Club Limited - the | Other services | 1959 |
| MPP (South Belfast and Lisburn) Ltd | Administrative & support | 2024 |
| MPP Mechanical Services Ltd | Construction | 2023 |
| MPS Contracts Ltd | Construction | 2017 |
| MPS NO1 Limited | Financial services | 2024 |
| MR Hospitality Ltd | Hospitality | 2021 |
| MSA Assets Ltd | Real estate | 2016 |
| MT Ventilation Services Limited | Construction | 2015 |
| MTF Tyres Ltd | Wholesale & retail | 2019 |
| Mulberry House Manufacturing Ltd | Manufacturing | 2020 |
| Mulligan Cleaning & Support Service Ltd | Administrative & support | 2017 |
| Mumtaz Sultana Limited | Health & social care | 2010 |
| Munal Tandoori Ltd | Hospitality | 2018 |
| Murphy Cars Ltd | Wholesale & retail | 2020 |
| Murray Motors (Belfast) Limited | Wholesale & retail | 2011 |
| Murray Motors Car Sales Ltd | Wholesale & retail | 2021 |
| Musgrave Healthcare Limited | Health & social care | 2014 |
| Musgrave House Holdings Ltd | Health & social care | 2025 |
| Mushroom Machine Company Limited | Manufacturing | 2014 |
| Mushroom Machine Hire Co Limited | Administrative & support | 2017 |
| Mushroom Manager Software Limited | Information & communication | 2019 |
| Mustard Seed Holdings Ltd | Professional & scientific | 2018 |
| MVV Metal Group LP | | 2022 |
| Mwei Ltd | Wholesale & retail | 2019 |
| Mwt-Rail Ltd | Professional & scientific | 2022 |
| MXI Properties Ltd | Real estate | 2024 |
| My Rest Ltd | Health & social care | 2022 |
| Myitdepartment Ltd | Information & communication | 2002 |
| Mypromopal Ltd | Information & communication | 2024 |
| Myrtlefield Trust - the | Education | 2008 |
| Mzuri Group Ltd | Financial services | 2018 |
| Mzuri Textiles Ltd | Manufacturing | 2024 |
| N Hope Consulting Ltd | Health & social care | 2025 |
| N-Tech Building Services Limited | Construction | 2018 |
| N.A.C Consultants Ltd | Professional & scientific | 2023 |
| N.I. Media Ltd | Information & communication | 1999 |
| N.I. Precision Ltd | Manufacturing | 2018 |
| N26 Property Ltd | Real estate | 2021 |
| N2N Canine Mills Limited | Manufacturing | 2022 |
| N4NETWORX Ltd | Information & communication | 2008 |
| Nail Artistry by Becca Ltd | Other services | 2025 |
| Nanobite (Number 6) Limited | Water & waste | 2018 |
| Nanobite Global Limited | Water & waste | 2016 |
| Nanobite Holdings Limited | Water & waste | 2015 |
| Nanobite International Limited | Water & waste | 2016 |
| Nanobite Limited | Water & waste | 2015 |
| Nanobite Technical Services Limited | Water & waste | 2015 |
| Nansen Street Holdings Ltd | Manufacturing | 2017 |
| Narvi Labs Ltd | Information & communication | 2026 |
| Nashama Ltd | Wholesale & retail | 2025 |
| Natax Healthcare Ltd | Administrative & support | 2025 |
| National Hospitality Group Ltd | Hospitality | 2021 |
| National Property Holdings Ltd | Real estate | 2022 |
| Natural Resilience Limited | Professional & scientific | 2025 |
| NDA Restaurants Limited | Hospitality | 2016 |
| Ndean Limited | Hospitality | 2012 |
| Ne&Co Limited | Professional & scientific | 2016 |
| Neal Robinson Ltd | Transport & logistics | 2019 |
| Near Shore Survey (NSS) Ltd | Professional & scientific | 2019 |
| Nebo International Limited | Administrative & support | 2018 |
| NEE’ Thai Takeaway Ltd | Hospitality | 2026 |
| Negative Waves Ltd | Information & communication | 2022 |
| Neighbour Two Five Ltd | Real estate | 2020 |
| Neil Cromie Accountancy Ltd | Professional & scientific | 2026 |
| NEM Distribution Ltd | Wholesale & retail | 2026 |
| Neocortica Ltd | Information & communication | 2015 |
| Neologic Products LP | | 2022 |
| Neosales Corp LP | | 2017 |
| Nest Build Ltd | Construction | 2019 |
| Nester Care Services NCS Ltd | Public administration | 2025 |
| NET Capital Services LLP | | 2018 |
| Netplus Technologies Limited | Information & communication | 2025 |
| Network Boxing & Fitness Ltd | Arts & recreation | 2020 |
| Neuland International Limited | Wholesale & retail | 2026 |
| Neuvo Limited | Wholesale & retail | 2025 |
| New Direction Signs & Graphics Ltd | Manufacturing | 2009 |
| New Horizon N.I Limited | Hospitality | 2024 |
| New Horizons Global Limited | Manufacturing | 2008 |
| New Modern Vision Limited | Professional & scientific | 2020 |
| New Web Ltd | Information & communication | 2021 |
| Newco Coffee Ltd | Wholesale & retail | 2018 |
| Newforge Autocare Ltd | Wholesale & retail | 2015 |
| Newrock Engineering Limited | Construction | 2009 |
| Newton Resources LLP | | 2018 |
| Newtownabbey Blow DRY Bar Limited | Other services | 2014 |
| Newwaysindustry LP | | 2021 |
| Next Move Online Ltd | Real estate | 2018 |
| Nextwave AI Solutions Ltd | Wholesale & retail | 2025 |
| Nexus Power Ltd | Construction | 2005 |
| NHA Property Limited | Households | 2023 |
| NI Auto Hub Ltd | Wholesale & retail | 2026 |
| NI Beauty Limited | Other services | 2025 |
| NI Beauty Services Ltd | Other services | 2024 |
| NI Holdings Ltd | Real estate | 2017 |
| NI Power Generation Limited | Energy | 2023 |
| NI Property Buyers Ltd | Real estate | 2025 |
| NI Property Letting Limited | Real estate | 2023 |
| NI Removals and Storage Ltd | Transport & logistics | 2021 |
| NI Services Ltd | Construction | 2023 |
| NI Total Building Services Ltd | Construction | 2016 |