| Millers Whitley Bay Limited | Financial services | 2020 |
| Millfield Media Ltd | Professional & scientific | 2013 |
| Milo K Limited | Health & social care | 2017 |
| Mimarc Construction Limited | Construction | 2004 |
| Mind Matters (Gary Simpson) Ltd | Education | 2023 |
| Mingulay Property Limited | Real estate | 2018 |
| Minimum Skincare Ltd | Wholesale & retail | 2020 |
| Misen Consulting Limited | Professional & scientific | 2011 |
| MIX & Mash Ltd | Hospitality | 2025 |
| MJ Integrity Ltd | Professional & scientific | 2018 |
| MJ Proctor Plastering Ltd | Construction | 2024 |
| MJM Joint Integrity Services Ltd | Mining & quarrying | 2022 |
| ML Redshaw Holdings Ltd | Financial services | 2020 |
| MLJ Events Ltd | Arts & recreation | 2018 |
| Mmcnet Limited | Wholesale & retail | 2021 |
| MME Sales UK Ltd | Wholesale & retail | 2023 |
| MMI Consulting Limited | Professional & scientific | 2017 |
| Mobile Location Based Services Limited | Information & communication | 2003 |
| Mobiltrax Ltd | Administrative & support | 2026 |
| Mocha Mondo Coffee Limited | Hospitality | 2013 |
| Mole Creative Ltd | Professional & scientific | 2022 |
| Moore Bros. the Shaw Ltd | Agriculture & fishing | 2004 |
| Moore House Holdings Ltd | Financial services | 2018 |
| Moorland Spirit Company Limited | Manufacturing | 2014 |
| Moorlands Residents Management Company Limited | Households | 2026 |
| Moovit (NE) Limited | Wholesale & retail | 2018 |
| Mopromedia Ltd | Professional & scientific | 2020 |
| Mor-Room Self Storage Limited | Transport & logistics | 2021 |
| Mor-Space Self Storage Limited | Transport & logistics | 2019 |
| Morpeth Accountants Limited | Extraterritorial | 2009 |
| Morpeth Bathrooms Limited | Wholesale & retail | 2021 |
| Morpeth Car Sales Ltd | Wholesale & retail | 2026 |
| Morpeth Couriers Ltd | Transport & logistics | 2010 |
| Morpeth Denture Clinic Limited | Health & social care | 2003 |
| Morpeth Electrical Services Ltd | Manufacturing | 2023 |
| Morpeth Holiday Camp Ltd | Health & social care | 2026 |
| Morpeth Kitchens and Interiors Company Limited | Other services | 2014 |
| Morpeth Lets Ltd | Administrative & support | 2021 |
| Morpeth Motor Company Ltd | Wholesale & retail | 2013 |
| Morpeth Old Fashioned Limited | Hospitality | 2025 |
| Morpeth Property Investments Ltd | Real estate | 1939 |
| Morpeth Road Car Sales Ltd | Wholesale & retail | 2026 |
| Morpeth Rugby Football Club Trading Ltd | Arts & recreation | 2025 |
| Morpeth Spice Tandoori Ltd | Hospitality | 2024 |
| Morpeth Studio Design Limited | Construction | 2023 |
| Morpeth Tandoori (Chantry) Ltd | Hospitality | 2014 |
| Morpeth Taxico Ltd | Transport & logistics | 2019 |
| Morpeth Town Academy Limited | Education | 2023 |
| Morpeth Van Hire Ltd | Administrative & support | 2023 |
| Morpeth Windows Company Limited | Construction | 2003 |
| Morwick Dairy Ice Cream | Manufacturing | 2013 |
| Motus Therapies Ltd | Health & social care | 2024 |
| Mouat Accountancy Limited | Professional & scientific | 2003 |
| Mouat of Morpeth Limited | Extraterritorial | 2022 |
| Mouldshaugh Farm Steading Management Company Limited | Households | 2006 |
| Mountain and Moss Ltd | Hospitality | 2021 |
| Mountain Skills Training Ltd | Arts & recreation | 2019 |
| MP Burgoyne Holdings Ltd | Financial services | 2023 |
| MPS North East Developments Limited | Other services | 2007 |
| MR Darren Liddle Limited | Extraterritorial | 2022 |
| MTP North East Developments Limited | Real estate | 2026 |
| Mudlarks Outdoors Ltd | Education | 2017 |
| Mulan (Morpeth) Ltd | Hospitality | 2014 |
| Mulger Investments Limited | Administrative & support | 2018 |
| Multi Trade Professionals Ltd | Construction | 2025 |
| Multivision Worldwide Limited | Professional & scientific | 2024 |
| Munro Planning and Development Ltd | Professional & scientific | 2025 |
| Munvaria Ltd | Professional & scientific | 2022 |
| Murray OIL & GAS Ltd | Mining & quarrying | 2019 |
| MVR Ltd | Wholesale & retail | 2025 |
| Mvsport Limited | Arts & recreation | 2013 |
| MW Legal Consult Ltd | Professional & scientific | 2025 |
| MWC Manufacturing Limited | Manufacturing | 2021 |
| MWS Properties (North East) LLP | | 2024 |
| MWS2 Properties Ltd | Real estate | 2018 |
| MWS3 Properties Ltd | Real estate | 2021 |
| My First Jewellery Box Limited | Wholesale & retail | 2000 |
| My Pet HQ Limited | Other services | 2016 |
| Mycpa Ltd | Wholesale & retail | 2008 |
| Myla-Jai's Hairsalon Ltd | Other services | 2023 |
| Mythril Financial Planning Ltd | Financial services | 2024 |
| Mzdent Limited | Health & social care | 2022 |
| N Harker Limited | Administrative & support | 2016 |
| N Wilson Limited | Information & communication | 2013 |
| N&C Property Holdings Limited | Real estate | 2022 |
| N. & F. Young (Decorating Services) Limited | Construction | 1976 |
| N.B. Clark Limited | Construction | 2015 |
| N.E Elevator Ltd | Manufacturing | 2025 |
| Nacho Average Dog Walk Ltd | Agriculture & fishing | 2025 |
| Narrow Nick (Rothbury) Ltd | Hospitality | 2016 |
| Nature's Way Physiotherapy Limited | Health & social care | 2023 |
| Navigator Catering Limited | Hospitality | 2025 |
| NDC Technical Services Ltd | Manufacturing | 2006 |
| NE Iconiqs Ltd | Wholesale & retail | 2026 |
| NE Recruitment Limited | Administrative & support | 2023 |
| NE Sport North East Ltd | Wholesale & retail | 2025 |
| Neay 611 Limited | Hospitality | 2022 |
| NEB2 Clean Ltd | Administrative & support | 2025 |
| Nedb Ltd | Professional & scientific | 2019 |
| Nedm Limited | Health & social care | 2019 |