| KCD Homes Limited | Construction | 2004 |
| Kelly New Homes Limited | Construction | 2001 |
| Key Inspirity Limited | Real estate | 2016 |
| Kids Kabin Drumaroad Limited | Education | 2003 |
| Kieran Mcpolin Ltd | Agriculture & fishing | 2026 |
| Killough Bay Oysters Ltd | Agriculture & fishing | 2026 |
| Kilnhill Contracts Ltd | Construction | 2024 |
| Knight Wood Estates 1 Limited | Real estate | 2020 |
| Knox Engineering Ltd | Construction | 2019 |
| Konnected Facilities Services Ltd | Information & communication | 2019 |
| KP Civil Ltd | Construction | 2019 |
| Kprm Property Ltd | Real estate | 2024 |
| Kylan One Limited | Real estate | 2018 |
| Kylan Two Limited | Real estate | 2020 |
| Kylmegan Limited | Real estate | 2017 |
| Kylmore Management Limited | Real estate | 2018 |
| Laurel Chlorination Ltd | Construction | 2008 |
| Laurel Farm Supplies Limited | Agriculture & fishing | 2020 |
| LEE & J Ltd | Hospitality | 2020 |
| Leitrim Community Playgroup | Education | 2004 |
| LEO Matheson Ltd | Construction | 2004 |
| Lime Grove (Castlewellan) Management Company Limited | Extraterritorial | 2006 |
| Loaded Street Food Ltd | Hospitality | 2025 |
| Local Taxis & Travel Limited | Transport & logistics | 2021 |
| Lucky EP 88 Ltd | Hospitality | 2026 |
| M Quinn Construction Ltd | Construction | 2020 |
| M. DEV Limited | Professional & scientific | 2012 |
| M3 Agency Distribution Ltd. | Wholesale & retail | 2017 |
| Macmillan Training Partnership Ltd | Education | 2026 |
| Magherasaul Homes Limited | Real estate | 2024 |
| Mahen Ltd | Hospitality | 2020 |
| Manrois Properties Ltd | Real estate | 2024 |
| Mark Gallagher Building Ltd | Construction | 2021 |
| Matthews Electrical Services (N.I.) Limited | Construction | 2016 |
| MC Cann's Award Winning Fish & Chips Ltd | Real estate | 2021 |
| Mcalerney Construction Services Ltd | Construction | 2014 |
| Mccartan CS Limited | Professional & scientific | 2023 |
| Mcgivern Logistics Ltd | Transport & logistics | 2025 |
| Mcpolin & Murdock (CA) Ltd | Professional & scientific | 2015 |
| Metis Initiatives C.I.C. | Education | 2016 |
| MF Carpentry & Joinery Ltd | Manufacturing | 2022 |
| Michelle Fahy Ltd | Health & social care | 2022 |
| Mill Hill Enterprise Park Limited | Other services | 2018 |
| Mimi by the Sea Ltd | Extraterritorial | 2021 |
| MJ Donnelly Quantity Surveyors Ltd | Construction | 2017 |
| MJ Oldbridge Developments Ltd | Construction | 2018 |
| MJD Building Ltd | Construction | 2018 |
| Mmcalern Limited | Agriculture & fishing | 2026 |
| Moneyslane Rural Community Hub | Arts & recreation | 2012 |
| Morgan Plumbing Services Ltd | Construction | 2017 |
| Motherbump Ltd | Education | 2025 |
| Mount Pleasant Trekking Limited | Arts & recreation | 2016 |
| Mourne Archery Limited | Arts & recreation | 2024 |
| Mourne Caravans Ltd | Administrative & support | 2020 |
| Mourne Energy Ltd | Administrative & support | 2025 |
| Mourne Horse & Pony Driving Club Limited | Arts & recreation | 2006 |
| Mourne Meadow Cabins Ltd | Hospitality | 2024 |
| Mourne Sport & Leisure Ltd | Arts & recreation | 2021 |
| Mourne Upvc Maintenance & Joinery Limited | Construction | 2019 |
| Mourne View Restaurants Limited | Hospitality | 2019 |
| Mrni Research Ltd | Professional & scientific | 1986 |
| MS Contracts (NI) Limited | Construction | 2005 |
| MT Contracts Ltd | Construction | 2024 |
| N M Joinery Contracts Ltd. | Construction | 2017 |
| Nalah Properties Limited | Real estate | 2018 |
| Naloda Property Holdings Ltd | Financial services | 2021 |
| Naman Consulting Limited | Information & communication | 2023 |
| Natural Stoneblock Ltd | Manufacturing | 2013 |
| Ndrl Ltd | Hospitality | 2025 |
| NEL Group Limited | Administrative & support | 2017 |
| Nexhyr Ltd | Information & communication | 2026 |
| NI Financial Directions Limited | Financial services | 2015 |
| NI Mechanical Group Ltd | Construction | 2017 |
| NI Mechanical Ltd | Construction | 2020 |
| Ni.Cbr Ltd | Wholesale & retail | 2026 |
| Niall & Jennifer Morgan Ltd | Agriculture & fishing | 2016 |
| Northpoint Hire Ltd | Construction | 2025 |
| Nuline Utilities Ltd | Construction | 2018 |
| Nuscreen Ltd | Construction | 2008 |
| O'Connor Bros Homes Limited | Construction | 2012 |
| O'Connor Homes Limited | Construction | 2020 |
| O'Hare Electrical Ltd | Construction | 2023 |
| O'Reilly Bricklaying Ltd | Construction | 2025 |
| Ocean Palace 2026 Ltd | Hospitality | 2026 |
| Ocean Palace Castlewellan Ltd | Hospitality | 2024 |
| Once Developments Ltd | Households | 2025 |
| OOC Properties Limited | Other services | 2025 |
| OPK Contracts Ltd | Construction | 2022 |
| Osborne Imaging Ltd | Health & social care | 2024 |
| Ouro Hot Honey Ltd | Manufacturing | 2024 |
| P and M Bricklaying Ltd | Construction | 2024 |
| P&G Agri Ltd | Agriculture & fishing | 2017 |
| P&R Property Development Ltd | Construction | 2004 |
| P. Mccartan & Sons Limited | Wholesale & retail | 1993 |
| Paradigm Niche Consulting Limited | Professional & scientific | 2021 |
| Patricia O'Rourke Limited | Wholesale & retail | 2026 |
| Paul Cunningham Contracts Ltd | Construction | 2016 |
| PD Plant Hire Ltd | Construction | 2017 |
| PDM Plumbing Services Ltd | Construction | 2018 |
| PH Stores Limited | Wholesale & retail | 2015 |