| Madlina Properties Ltd | Real estate | 2022 |
| Magik Properties Ltd | Real estate | 2023 |
| Magnesia Studios Limited | Arts & recreation | 2025 |
| Magpie Embedded Limited | Information & communication | 2020 |
| Magpie Horseshoes Limited | Manufacturing | 2023 |
| Majestic Boxing Ltd. | Arts & recreation | 2016 |
| Malbarr Developments Limited | Real estate | 2007 |
| MAN Power Music Ltd | Professional & scientific | 2024 |
| Management of 2 York Terrace Limited | Real estate | 2001 |
| MAP Holdings NE Ltd | Manufacturing | 2021 |
| MAP Telecoms Ltd | Information & communication | 2020 |
| Mapleleaf (Northern) Limited | Real estate | 2003 |
| Mapleleaf Commercial Maintenance Limited | Construction | 2018 |
| Mapp Systems Limited | Manufacturing | 2001 |
| Maps Consulting Limited | Professional & scientific | 2025 |
| Marden Amateur Boxing Club CIC | Arts & recreation | 2023 |
| Marfam Group Ltd | Professional & scientific | 2020 |
| Marinahair Ltd | Other services | 2024 |
| Marine Chandlery Limited | Other services | 2024 |
| Mark Christie Offshore Limited | Administrative & support | 2016 |
| Mark Gibson Wind Ltd | Professional & scientific | 2023 |
| Mark Patterson Financial Planning Limited | Professional & scientific | 2019 |
| Marmstrong Offshore Ltd | Construction | 2025 |
| Mars Projects Group Ltd | Professional & scientific | 2024 |
| Marsden's Mechanical Engineering Limited | Professional & scientific | 2026 |
| Marshall.A Services Limited | Mining & quarrying | 2024 |
| Martin Wright Consulting Ltd | Professional & scientific | 2025 |
| Martineau House Ltd | Hospitality | 2022 |
| Mason Residential 2024 Limited | Real estate | 2024 |
| Mason Resourcing Ltd | Administrative & support | 2024 |
| Matrix Investment Partners Limited | Other services | 2018 |
| Matthew Temple Limited | Professional & scientific | 2021 |
| Mavens Media Limited | Information & communication | 2023 |
| Maxi Coin Ltd | Administrative & support | 2010 |
| Maximal Group Ltd | Wholesale & retail | 2024 |
| Mayfairpropertygroup Limited | Construction | 2013 |
| Maygee Ltd | Professional & scientific | 2026 |
| Mayhem Consults Limited | Professional & scientific | 2023 |
| MB & SB KHANVENIENCE-786 Building Company Ltd | Construction | 2019 |
| MBS North East Ltd | Administrative & support | 2019 |
| MC Sports Coaching Ltd | Arts & recreation | 2022 |
| Mcalinden Group Ltd | Real estate | 2026 |
| MCG Smart Renovations Ltd | Construction | 2026 |
| Mcgregor Associates Limited | Professional & scientific | 2011 |
| Mclaughlin & Ling Reforestation Limited | Agriculture & fishing | 2020 |
| Mclee Investments Limited | Real estate | 2021 |
| MCM Sheetmetal Work Ltd | Other services | 2018 |
| Mcmaster Hospitality Solutions Ltd | Hospitality | 2020 |
| Mcneill Creative UK Limited | Wholesale & retail | 2023 |
| Mconnected Ltd | Information & communication | 2013 |
| Meadow Well Connected | Information & communication | 1997 |
| Mechanical Installations North East Limited | Manufacturing | 2025 |
| Mechanical Sroka Services Ltd | Professional & scientific | 2024 |
| Mectronic Instruments Limited | Manufacturing | 1972 |
| Median UK Services Limited | Professional & scientific | 2016 |
| Medicdj Limited | Health & social care | 2024 |
| Medicode Ltd | Information & communication | 2026 |
| Medloop Limited | Administrative & support | 2018 |
| Meer VIP Barbers Ltd | Other services | 2025 |
| Meet ME on the Corner Cafe Ltd | Hospitality | 2022 |
| MEG - Mindful Educational Guidance Limited | Education | 2026 |
| Meghan Bell Limited | Health & social care | 2025 |
| Melling Media Ltd | Information & communication | 2016 |
| Melrose House Cullercoats Ltd | Health & social care | 2012 |
| Memorial Works Holdings Limited | Real estate | 2023 |
| MEN of Mellness Ltd | Construction | 2025 |
| Mentorslearningacademy(Mla) Limited | Education | 2025 |
| MEP Design Ltd | Professional & scientific | 2023 |
| Merchants Properties Ltd | Real estate | 2023 |
| Mercu IT Solutions Ltd | Information & communication | 2019 |
| Merlin Residential Limited | Real estate | 2024 |
| Merrilees Consultant Services Ltd | Professional & scientific | 2011 |
| Merryweather Holdings Ltd | Construction | 2025 |
| Merwyn Ltd | Administrative & support | 2017 |
| Metis Therapy Limited | Health & social care | 2014 |
| MGD TM Ltd | Construction | 2017 |
| MH Transport Limited | Transport & logistics | 2025 |
| MHW Engineering Limited | Manufacturing | 2022 |
| Michael Milonas Ltd | Construction | 2024 |
| Michael Seery Financial Planning Limited | Professional & scientific | 2020 |
| Michelle Oxley Estate Planning Limited | Professional & scientific | 2026 |
| Microtyne Ltd | Information & communication | 2022 |
| Mighty Mortar Limited | Construction | 2018 |
| Mila’S Salon Ltd | Other services | 2026 |
| Milburn Consulting Limited | Information & communication | 2016 |
| Mildenhill Estates Ltd | Households | 2010 |
| Miley & Johnson Active Kids Club Ltd | Health & social care | 2024 |
| Millgrove IT Ltd | Information & communication | 2015 |
| Mindful Meets Ltd | Health & social care | 2023 |
| Minhoco 75 Limited | Financial services | 2022 |
| Miss Tallett Limited | Professional & scientific | 2012 |
| Missed Call Mate Ltd | Information & communication | 2025 |
| Mister Ridleys Limited | Hospitality | 2014 |
| Mitchinson Ltd | Real estate | 2022 |
| Mitom Properties Limited | Real estate | 2003 |
| MJ Graham Plumbing & Heating Limited | Construction | 2006 |
| MJL Property Investments Ltd | Real estate | 2024 |
| Mjpower Services Ltd | Construction | 2021 |
| MJW Safety Services Limited | Professional & scientific | 2024 |
| MK Plumbing Solutions Ltd | Construction | 2020 |