| Maja Property Limited | Real estate | 2022 |
| Makarios Accounting Limited | Professional & scientific | 2019 |
| Makarios Properties Limited | Real estate | 2019 |
| Mallan & Howard Ltd | Construction | 2025 |
| Mallan Plant Services Ltd | Administrative & support | 2024 |
| Mamjam Media Ltd | Information & communication | 2014 |
| Mannings of Alnwick Limited | Wholesale & retail | 2016 |
| Manufacture Change Limited | Professional & scientific | 2005 |
| Marc Anthony's UK Limited | Wholesale & retail | 2021 |
| Marilyn and Melrose Limited | Wholesale & retail | 2023 |
| Marina View Hotel Limited | Hospitality | 2026 |
| Marjorie Limited | Real estate | 2021 |
| Market Street Apartments Ltd | Hospitality | 2024 |
| Marsh Business Transformation Ltd | Professional & scientific | 2014 |
| Marshall Tractors Limited | Wholesale & retail | 2012 |
| Martin PUB Company Limited | Hospitality | 2025 |
| Mastora Limited | Wholesale & retail | 2010 |
| Mckennas Catering Ltd | Hospitality | 2007 |
| Meds and ME Ltd | Wholesale & retail | 2021 |
| MEG Fletcher Ltd | Arts & recreation | 2024 |
| Melvyn's Cafe Ltd | Hospitality | 2025 |
| Mermelada Limited | Hospitality | 2022 |
| Michael Laird Architects NW Limited | Professional & scientific | 2023 |
| Michie Group LLP | | 2025 |
| Middle Cawledge Holiday Lets Ltd | Real estate | 2025 |
| Middleton Estates and Lettings Ltd | Real estate | 2024 |
| MJ & MR Properties Ltd | Real estate | 2023 |
| Moffat Water Game Limited | Wholesale & retail | 2009 |
| Monty Technologies Limited | Information & communication | 2026 |
| Mori Arts Ltd | Information & communication | 2021 |
| Morris & Plumley (Northumberland) Limited | Professional & scientific | 2016 |
| Mothers Cupboard Ltd | Other services | 2021 |
| Mouldshaugh Farm Limited | Agriculture & fishing | 1964 |
| Msgworks Ltd. | Professional & scientific | 2014 |
| Mylife Productions 2013 CIC | Information & communication | 2012 |
| Myrmidon Books Limited | Information & communication | 2005 |
| N J & R Dods Limited | Agriculture & fishing | 2009 |
| N P Building Services (Amble) Ltd | Manufacturing | 2021 |
| N&P Plumbing and Heating Services Limited | Construction | 2008 |
| N. Mundy Limited | Other services | 2018 |
| Nanna Pat's Cafe and Bistro Ltd | Hospitality | 2023 |
| Nanna Pat's Food Shack Ltd | Hospitality | 2026 |
| Narrow Nick Limited | Hospitality | 2024 |
| Narrowgate Indian Ltd | Hospitality | 2023 |
| NC Firesafe Ltd. | Public administration | 2013 |
| NE Construction Ltd | Construction | 2008 |
| NE Electrics Ltd | Construction | 2008 |
| Nelson's Cleaning Services Ltd | Administrative & support | 2025 |
| Nest 78 Ltd | Professional & scientific | 2023 |
| Neurogenics Ltd | Manufacturing | 2015 |
| New Schooner Hotel Ltd | Hospitality | 2017 |
| Newby Station Limited | Extraterritorial | 2009 |
| Newcastle House Hotel Limited | Hospitality | 2019 |
| Newplatform.Art | Administrative & support | 2017 |
| Newplatform.Art Trading Limited | Arts & recreation | 2017 |
| Next Generation Business (NE) Limited | Administrative & support | 2018 |
| NGO Training Ltd | Education | 2004 |
| Nice Pair Limited | Wholesale & retail | 2022 |
| NO Limits Health Clubs Ltd. | Administrative & support | 2002 |
| Nofy Ltd | Other services | 2022 |
| North by Design Ltd | Professional & scientific | 2023 |
| North by North East Print and Sign Limited | Manufacturing | 2019 |
| North Country Inns Limited | Hospitality | 2015 |
| North East Assistance and Therapy Dogs CIC | Other services | 2025 |
| North East Equality & Diversity Limited | Health & social care | 2006 |
| North East Escapes Limited | Hospitality | 2024 |
| Northern Angels NE Ltd | Wholesale & retail | 2022 |
| Northern Fencing and Landscaping Ltd | Professional & scientific | 2023 |
| Northern Force Ltd | Construction | 2025 |
| Northern Fortress Limited | Construction | 2019 |
| Northern Game Ltd | Wholesale & retail | 2020 |
| Northern Lodges (UK) Ltd. | Hospitality | 2009 |
| Northern Property Finance Limited | Financial services | 2004 |
| Northern Sanctuaries UK Ltd | Real estate | 2025 |
| Northumberland Accountants Limited | Professional & scientific | 2013 |
| Northumberland Aviation Ltd | Transport & logistics | 2023 |
| Northumberland Community Development Company | Information & communication | 2003 |
| Northumberland Community Digital Community Interest Company | Information & communication | 2023 |
| Northumberland Cottages Ltd | Hospitality | 2017 |
| Northumberland Dental Implants Limited | Health & social care | 2017 |
| Northumberland Estates Property Enterprises | | 2003 |
| Northumberland Green Ltd | Agriculture & fishing | 2022 |
| Northumberland Havens Ltd | Hospitality | 2026 |
| Northumberland Holidays (UK) Ltd | Administrative & support | 2013 |
| Northumberland Management Services Limited | Construction | 2020 |
| Northumberland Properties (Alnwick) Ltd | Real estate | 2023 |
| Northumberland Property Lets Ltd | Real estate | 2020 |
| Northumberland Real Estates Limited | Households | 2026 |
| Northumberland Spirit Company Ltd | Manufacturing | 2016 |
| Northumbria Brickwork Ltd | Construction | 2015 |
| Northumbria Coatings Ltd | Construction | 2022 |
| Northumbria Pets Limited | Other services | 2024 |
| Northumbrian Estates Limited | Real estate | 2026 |
| Northumbrian Industrial Mission Ltd | Other services | 2021 |
| Northumbrian Natural Capital Solutions Ltd | Agriculture & fishing | 2021 |
| Northumbrian Property Maintenance Ltd | Construction | 2013 |
| Novo Theatre Ltd. | Arts & recreation | 1991 |
| NS Group PVT Ltd | Wholesale & retail | 2023 |
| NU Urban Limited | Professional & scientific | 2015 |
| Oakes Chamberlain Medical Ltd | Health & social care | 2025 |