| MK Naturals Ltd | Manufacturing | 2025 |
| ML City Brickwork Ltd | Construction | 2025 |
| ML Enterprises Limited | Professional & scientific | 2020 |
| Mmcc Bricklaying Ltd | Construction | 2022 |
| MMG Contracts Ltd | Construction | 2010 |
| MMG Investments Ltd | Financial services | 2024 |
| MMG Joinery Works Ltd | Construction | 2019 |
| MMS NI Ltd | Wholesale & retail | 2003 |
| Moat Group Holdings Ltd | Financial services | 2021 |
| Moat Holdings Ltd | Financial services | 2022 |
| MOK (Northern Ireland) Limited | Extraterritorial | 2014 |
| Monarch Stationery Ltd | Wholesale & retail | 2024 |
| Moneynick EP Limited | Real estate | 2022 |
| Mount Leisure Limited | Hospitality | 2021 |
| MRS Lee's Little Bees Ltd | Health & social care | 2019 |
| MTJ Insights Ltd | Professional & scientific | 2025 |
| MTN Property Holdings Limited | Real estate | 2022 |
| MTN Property Investments Limited | Construction | 2020 |
| Muckamore Parish Development Association | Extraterritorial | 2023 |
| Muckamore Rope Access Limited | Construction | 2026 |
| Mulholland Maxus Limited | Wholesale & retail | 2025 |
| Mulholland Motor Exchange Limited | Wholesale & retail | 2019 |
| Murphy Welds Limited | Professional & scientific | 2025 |
| Mutex Markets Ltd | Information & communication | 2016 |
| MWD Haulage Ltd | Transport & logistics | 2022 |
| Mynurserypal Ltd | Information & communication | 2015 |
| Nails by SG Limited | Other services | 2017 |
| Nantra LLP | | 2023 |
| Native African Asian Foods Ltd | Wholesale & retail | 2023 |
| Nc&Ll Properties Ltd | Real estate | 2024 |
| NCL Innovate Ltd | Wholesale & retail | 2024 |
| Neeson Tooling Services Limited | Manufacturing | 2020 |
| Neptune Travel Limited | Administrative & support | 2005 |
| Nest Rests Limited | Real estate | 2025 |
| NET Technologies Limited | Construction | 2024 |
| Netzero Alchemists Limited | Professional & scientific | 2024 |
| Newbridge Joinery Limited | Manufacturing | 2006 |
| Newferry Limited | Wholesale & retail | 2016 |
| Newferry Properties Limited | Real estate | 2017 |
| Nextus Agency Ltd | Administrative & support | 2025 |
| Nextwaveoutdoor Ltd | Education | 2025 |
| NHH Private Medical Services Ltd | Health & social care | 2022 |
| NI Cleaning Services Ltd | Administrative & support | 2022 |
| NI Counselling & Associates Limited | Health & social care | 2023 |
| NI Merchants Limited | Wholesale & retail | 2018 |
| NI Van Sales Ltd | Wholesale & retail | 2020 |
| Nicola Kielt Limited | Health & social care | 2014 |
| Nioss Ltd. | Information & communication | 2017 |
| Nitec Solutions Ltd | Information & communication | 1998 |
| NLB Mcneilly Consulting Ltd | Agriculture & fishing | 2020 |
| NMK Promotions Ltd | Manufacturing | 2018 |
| Noor & Insha Ltd | Wholesale & retail | 2026 |
| Norana Ltd | Wholesale & retail | 2026 |
| Norman Emerson Group Limited | Mining & quarrying | 1970 |
| Norridge System LLP | | 2014 |
| North Channel Timber Limited | Manufacturing | 2023 |
| Northern Academy of Dental Implants Ltd | Health & social care | 2025 |
| Northern Cardiology Ltd | Health & social care | 2010 |
| Northern Farm Supplies Ltd | Agriculture & fishing | 2010 |
| NW Aero Servises Limited | Professional & scientific | 2023 |
| NWA Engineering Limited | Professional & scientific | 2019 |
| Nyvexa Ltd | Wholesale & retail | 2026 |
| O'Donoghue Vehicles (N.I.) Limited | Wholesale & retail | 2024 |
| Oakfield Cabinets Ltd | Manufacturing | 2005 |
| OBL Properties Limited | Real estate | 2023 |
| Odibende Ltd | Health & social care | 2023 |
| OG Valves Ltd | Wholesale & retail | 2024 |
| Old Mill Dental LAB Limited | Manufacturing | 2024 |
| OMC Couriers Limited | Administrative & support | 2002 |
| OMNI26 Ltd | Other services | 2026 |
| ONB Contracts Limited | Construction | 2012 |
| ONB Homes Limited | Construction | 2020 |
| One 2 One Care & Support Services (NI) Ltd | Health & social care | 2014 |
| Opadoo Limited | Extraterritorial | 2024 |
| Oran Mcauley Ltd | Financial services | 2019 |
| Orco Holdings Limited | Financial services | 2022 |
| Ordersboss Ltd | Information & communication | 2025 |
| Orta Europe Ltd | Professional & scientific | 2025 |
| OSG Cloud Limited | Information & communication | 2000 |
| OSG Topco Limited | Financial services | 2025 |
| OSP Wholesale Ltd | Wholesale & retail | 2022 |
| OTB Engineering Design (NI) Ltd | Professional & scientific | 2022 |
| OUT of the Woods Event Catering Limited | Hospitality | 2025 |
| Outsource AI Limited | Information & communication | 2024 |
| Outsource Group Holdings Limited | Information & communication | 2021 |
| Outsource Group Limited | Information & communication | 2022 |
| Outsource Online LLP | | 2011 |
| Outsource Online Services Ltd | Information & communication | 2020 |
| Ownterms Limited | Information & communication | 2019 |
| Ozeire Timber Limited | Construction | 2007 |
| P & J Walls Limited | Mining & quarrying | 2015 |
| P & S Plastering Contractors Limited | Construction | 2018 |
| P M Preda Belfast Limited | Wholesale & retail | 2021 |
| P Mcvey Building Systems Ltd | Construction | 2015 |
| P&D Kelly's Bar Ltd | Hospitality | 2022 |
| P&S Specialist Joinery Limited | Manufacturing | 2026 |
| P.&J. Mccann Holdings Limited | Financial services | 1983 |
| PAK Distribution Ltd | Wholesale & retail | 2014 |
| Parkgate Farm and Cafe Ltd | Agriculture & fishing | 2022 |
| Pascal Holdings Unlimited | Financial services | 2022 |