| Mbsp Interiors Limited | Construction | 2023 |
| MC Consultancy and Management Ltd | Professional & scientific | 2021 |
| Mccarrick Homes Ltd | Construction | 2008 |
| MD Autoservices Ltd | Wholesale & retail | 2016 |
| MDC Project Solutions Limited | Construction | 2024 |
| MDG Consultants Limited | Professional & scientific | 2023 |
| ME Sweets Ltd | Wholesale & retail | 2025 |
| Meat Zone UK Limited | Manufacturing | 2002 |
| Medlife Care Ltd | Health & social care | 2018 |
| Medsolve (UK) Limited | Administrative & support | 2015 |
| Medsolve Complex Care Limited | Administrative & support | 2024 |
| MEE (NE) Ltd | Hospitality | 2019 |
| MEL Lydon Mortgage Solutions Ltd | Financial services | 2019 |
| Memories of India (NE) Ltd | Hospitality | 2019 |
| Memories of India Ltd | Hospitality | 2024 |
| Memoriez of India Ltd | Hospitality | 2025 |
| Memre Ltd | Information & communication | 2024 |
| Mental Health Safety UK Limited | Health & social care | 2019 |
| Meraki Reiki CIC | Other services | 2025 |
| Meridian Arts and Crafts Ltd | Wholesale & retail | 2024 |
| Metts Media Limited | Administrative & support | 2025 |
| Mgawel Property Ltd | Construction | 2024 |
| Mias Takeaway Ltd | Hospitality | 2022 |
| Michael Lawrence Management Limited | Real estate | 2014 |
| Mihai Construct Ltd | Construction | 2025 |
| Miles Holdings Limited | Financial services | 2018 |
| Minotaur Commercial Services Ltd | Administrative & support | 2020 |
| Mira Victory Shine Ltd | Hospitality | 2025 |
| Mischief Tattoo Studio Limited | Other services | 2023 |
| Mishreki Healthcare Limited | Health & social care | 2019 |
| Miss Elephant Ltd | Hospitality | 2018 |
| Mitch Rewinds Ltd | Manufacturing | 2019 |
| Mj&Rc Developments Ltd | Real estate | 2020 |
| MJF Bathroom & Construction Services Ltd | Construction | 2025 |
| MJS Computers Limited | Other services | 2019 |
| MJS Construction/Rope Access Services Limited | Construction | 2016 |
| MJSMITH85 Ltd | Transport & logistics | 2023 |
| MK Builders (NE) Limited | Construction | 2023 |
| MK Property Development Ltd | Construction | 2011 |
| MK Youth Sports CIC | Wholesale & retail | 2021 |
| ML Heat & Renewables Ltd | Construction | 2024 |
| MLG Property Services Ltd | Real estate | 2025 |
| MLL Elmwood Limited | Real estate | 2024 |
| MLM Estates Ltd | Real estate | 2023 |
| MNO Developments Limited | Real estate | 2017 |
| Moarmjp Ltd | Hospitality | 2024 |
| Mobile Elements (Accessories) Ltd | Wholesale & retail | 2021 |
| Modas Safety Solutions Limited | Other services | 2007 |
| Modex Security Cctv Systems Ltd | Administrative & support | 2019 |
| Mona Lisa Arts & Media Community Interest Company | Arts & recreation | 2009 |
| Montrose Scotch Whisky Ltd. | Manufacturing | 1973 |
| Monument Cars Limited | Wholesale & retail | 2024 |
| Moobears Chester LE Street Limited | Arts & recreation | 2018 |
| Morley Services Limited | Extraterritorial | 2017 |
| Morris Store Ltd | Wholesale & retail | 2025 |
| Movin Legal Limited | Information & communication | 2015 |
| MR D Detailing Limited | Administrative & support | 2025 |
| MR Mars Properties Ltd | Real estate | 2025 |
| Mr.Fish&Chicken Ltd | Hospitality | 2025 |
| MSJ Creative Limited | Professional & scientific | 2019 |
| Multicrown Properties Limited | Real estate | 2002 |
| Murray Holdings (North East) Limited | Real estate | 2018 |
| Murton VIC Developments Limited | Construction | 2018 |
| Muscari Events Limited | Wholesale & retail | 2024 |
| Musicwonders.Org Community Interest Company | Education | 2013 |
| MW Autism Consultancy Ltd | Education | 2019 |
| My Dog Barber (CLS) Limited | Other services | 2019 |
| My Dog Barber (Holdings) Limited | Financial services | 2024 |
| My Dog Barber (Jesmond) Limited | Other services | 2023 |
| My Dog Barber Academy Limited | Other services | 2024 |
| My Masala Ltd | Hospitality | 2024 |
| My Masala Private Ltd | Hospitality | 2026 |
| My Old Dad's Honey Ltd | Manufacturing | 2024 |
| My Spice CLS Ltd | Hospitality | 2024 |
| Mybe Awards Ltd | Hospitality | 2017 |
| Mzuri Medical Limited | Health & social care | 2018 |
| N&G Donnelly Holdings Limited | Financial services | 2022 |
| N&Y Radbourne Properties Limited | Real estate | 2017 |
| N.J.Z Properties Limited | Real estate | 2024 |
| N2 Project Solutions Limited | Professional & scientific | 2017 |
| Nagaspice One Limited | Hospitality | 2025 |
| Natalia Jordan Ltd | Other services | 2023 |
| Nathan Hodgson Ltd | Information & communication | 2025 |
| National Rail Bishop Auckland Ltd | Transport & logistics | 2018 |
| Nationwide Splicing & Rope Services Limited | Manufacturing | 1992 |
| NC Educational Psychology Ltd | Education | 2023 |
| NDC Associates Ltd | Professional & scientific | 2006 |
| NE Entertainment & Events Ltd | Arts & recreation | 2026 |
| NE1 for Joinery Ltd | Construction | 2018 |
| NE36 Property Partners Limited | Real estate | 2020 |
| Nechambers Limited | Professional & scientific | 2023 |
| Needle & Lash Limited | Other services | 2023 |
| Nelson Properties Durham LLP | | 2025 |
| Neuroactiveuk Ltd | Health & social care | 2015 |
| Nevis Property Management Limited | Real estate | 2016 |
| New Coxhoe Nursery Ltd | Agriculture & fishing | 2021 |
| New Living Properties Ltd | Real estate | 2022 |
| New Nutrition Company Limited | Wholesale & retail | 2019 |
| New Vision Care Services Limited | Public administration | 2018 |
| Newater Ltd | Professional & scientific | 2013 |