| Mani Recycling Limited | Wholesale & retail | 2022 |
| MANI2011 Limited | Wholesale & retail | 2015 |
| Mannshanks Ltd | Professional & scientific | 2023 |
| Marina West Amble Management Company Ltd | Households | 2023 |
| Marine Parade Gorleston Limited | Real estate | 2019 |
| Marixia Limited | Information & communication | 2026 |
| Market Collective Community Interest Company | Administrative & support | 2024 |
| Marolu Ltd | Real estate | 2020 |
| Maurice Robson Limited | Transport & logistics | 2014 |
| Max-Vape Limited | Wholesale & retail | 2017 |
| Maydia Limited | Arts & recreation | 2019 |
| Maza Homes Ltd | Hospitality | 2019 |
| Mcmahon's & Iplumb Ltd | Construction | 2016 |
| Mech Services Limited | Professional & scientific | 2018 |
| Megastone Limited | Manufacturing | 2000 |
| Meiros Properties Ltd | Extraterritorial | 2021 |
| Metcalf Ltd | Manufacturing | 2014 |
| Meytamechta Ltd | Wholesale & retail | 2025 |
| Mezala Curry House Ltd | Hospitality | 2024 |
| MG Enterprise Holdings Limited | Hospitality | 2026 |
| Michael Summers Properties Ltd | Real estate | 2025 |
| Michael Wood Design Limited | Administrative & support | 2010 |
| Michal's Gym Ltd | Arts & recreation | 2022 |
| Mick Cowan Engineering Services Limited | Professional & scientific | 2015 |
| Midlands Electrical Solutions Ltd | Construction | 2026 |
| Mielnik Ltd | Other services | 2013 |
| Mike Rogerson Estate Agents Limited | Real estate | 2001 |
| Mike Rogerson Lettings Limited | Real estate | 2025 |
| Mike Rogerson Limited | Extraterritorial | 2005 |
| Milburn Motors Garages Limited | Wholesale & retail | 1982 |
| Milburn Storage Ltd | Other services | 2015 |
| Millies Commercial Cleaning Ltd | Administrative & support | 2018 |
| Millview Group Ltd | Information & communication | 2022 |
| Minhoco 91 Limited | Financial services | 2025 |
| Minhoco 92 Limited | Financial services | 2025 |
| Minnie Cabs Ltd | Transport & logistics | 2018 |
| Mistura Enterprise Limited | Health & social care | 2009 |
| Mistura Holdings Ltd | Financial services | 2024 |
| Mistura Informatics Ltd | Health & social care | 2011 |
| Mjje Solutions Limited | Professional & scientific | 2015 |
| MJS Technical Services Ltd | Professional & scientific | 2025 |
| MJY23 Ltd | Wholesale & retail | 2023 |
| Moby Dicks Fish Bar Limited | Wholesale & retail | 2014 |
| Modaxa Limited | Administrative & support | 2022 |
| Mohammad Munir Zazai Ltd | Wholesale & retail | 2025 |
| Mohammad Nasir Zazai Ltd | Wholesale & retail | 2025 |
| Monarch Analysis Limited | Extraterritorial | 1995 |
| Montane Ltd | Manufacturing | 1996 |
| Monza Sports Tuning Limited | Wholesale & retail | 2003 |
| Moods Hairdressing Ltd | Administrative & support | 2019 |
| Morpeth Health & Beauty Rooms Ltd | Real estate | 2022 |
| Morpeth Plumbing & Heating Ltd | Construction | 2006 |
| Morpeth Road Motors Ltd | Wholesale & retail | 2025 |
| Mortal Fools | Education | 2012 |
| Mpatel Trading and Consultancy Ltd | Wholesale & retail | 2026 |
| MR S Butters Limited | Construction | 2005 |
| Mrea (Ashington) Ltd | Real estate | 2011 |
| Mrea (Bedlington) Ltd | Extraterritorial | 2016 |
| Mrea (Blyth) LLP | | 2014 |
| Mrea (Morpeth) Ltd | Real estate | 2019 |
| Mrea (North Tyneside) LLP | | 2010 |
| Msmcculloch Ltd | Professional & scientific | 2022 |
| MXG Solutions Ltd | Construction | 2026 |
| My Barber Salon Ltd | Other services | 2026 |
| My Wealth Tree Limited | Financial services | 2020 |
| Mysboutique UK Ltd | Manufacturing | 2017 |
| Möbru Limited | Wholesale & retail | 2019 |
| N Warnes & SON North East Ltd | Manufacturing | 2025 |
| National Property Surveyors (UK) Ltd | Administrative & support | 2014 |
| Ncea Trading Ltd | Education | 2021 |
| NCL Imports Ltd | Wholesale & retail | 2024 |
| NE Auto Salvage Ltd | Wholesale & retail | 2025 |
| NE Tiger Limited | Hospitality | 2026 |
| Ne-Competitions Ltd | Wholesale & retail | 2025 |
| NE1 Commercials Ltd | Extraterritorial | 2019 |
| NE63 Business Group Ltd | Hospitality | 2016 |
| Nehd Ltd | Professional & scientific | 2016 |
| NEM Limited | Administrative & support | 2012 |
| Nepsychology Ltd | Health & social care | 2022 |
| Nesika Retails Ltd | Wholesale & retail | 2021 |
| Networks Centre Limited | Information & communication | 2005 |
| New Heavenly Chinese Takeaway Limited | Hospitality | 2014 |
| New-Tec Developments Limited | Construction | 2017 |
| Newtricks Advanced Business Training Ltd | Administrative & support | 2006 |
| Nisa Hand Carwash (NE) Ltd | Other services | 2022 |
| Nisa Hand Carwash Ltd | Extraterritorial | 2018 |
| NMT Food Limited | Hospitality | 2025 |
| North Creek Investments Limited | Real estate | 2018 |
| North East Caravans Limited | Wholesale & retail | 2004 |
| North East Economic Forum Limited | Other services | 2007 |
| North East Metals Limited | Water & waste | 2015 |
| North Edge Roofing Ltd | Construction | 2026 |
| Northeast TYT Bolts Ltd | Mining & quarrying | 2026 |
| Northern Motor Services Ltd | Wholesale & retail | 2025 |
| Northern Sun Beds Ltd | Manufacturing | 2025 |
| Northern Teeth Laboratory Ltd | Health & social care | 2026 |
| Northern Training Partnership Limited | Administrative & support | 2001 |
| Northumberland Business Service Limited | Administrative & support | 2000 |
| Northumberland Church of England Academy Trust | Education | 2008 |
| Northumberland Commercial Ltd | Real estate | 2021 |