| Memphis North East Limited | Wholesale & retail | 2022 |
| Menocool Ltd | Wholesale & retail | 2025 |
| Menosleep Ltd | Wholesale & retail | 2025 |
| Menstrual Rage Ltd | Arts & recreation | 2021 |
| Mental Health Matters | Health & social care | 1984 |
| Mental Health Solutions Limited | Health & social care | 2010 |
| Merciless Fight Promotions Ltd | Arts & recreation | 2026 |
| Mercury Marketing Associates Limited | Other services | 2002 |
| Meridian Peptides Ltd | Wholesale & retail | 2026 |
| Mermedia Limited | Professional & scientific | 2024 |
| Merrills Fish Grill Limited | Administrative & support | 2020 |
| MES Construction North East Ltd | Construction | 2021 |
| Mess Property Services Limited | Real estate | 2018 |
| Meta Facades Limited | Professional & scientific | 2022 |
| Metaedx Ltd | Extraterritorial | 2025 |
| Metaedx Technologies Ltd | Information & communication | 2025 |
| Metcalfe Components (Sunderland) Limited | Professional & scientific | 1976 |
| Metters Maintenance Limited | Construction | 2025 |
| Mettersproperties Ltd | Real estate | 2023 |
| MEXICO70 Limited | Hospitality | 2023 |
| MF Building Services NE Limited | Construction | 2022 |
| MF Properties NE Limited | Real estate | 2025 |
| MF Waste Services Ltd | Water & waste | 2025 |
| MGE Electrical Ltd | Construction | 2013 |
| MGH Decorators Ltd | Construction | 2018 |
| MGH Takeaway Ltd | Hospitality | 2023 |
| MGP Developments Ltd | Real estate | 2024 |
| MH Decorators and Developments Ltd | Construction | 2025 |
| MH Market Ltd | Wholesale & retail | 2026 |
| MI Local Trades Ltd | Administrative & support | 2025 |
| MIA MV Ltd | Wholesale & retail | 2012 |
| Miah Tandoori Ltd | Administrative & support | 2019 |
| Michael Coghlan Football Coaching - 3V3 Ltd | Arts & recreation | 2025 |
| Michael Erskine CIC | Health & social care | 2025 |
| Michael Fairweather Limited | Administrative & support | 2018 |
| Michael Hodgson Limited | Real estate | 2011 |
| Michael Homes Ltd | Construction | 2025 |
| Michael IAN Curry Ltd | Extraterritorial | 2024 |
| Michael Jameson Ltd | Administrative & support | 2025 |
| Michael Lane T/A Kitchens Komplete Limited | Wholesale & retail | 2024 |
| Michael Maddison Consultancy Ltd | Professional & scientific | 2016 |
| Michael Parkin MMA Ltd | Arts & recreation | 2023 |
| Michael Young Enterprises Ltd | Financial services | 1998 |
| Michaelangelo's of Durham Limited | Hospitality | 2001 |
| Michelle's Limited | Hospitality | 2026 |
| Michelle's Postal Services Limited | Wholesale & retail | 2026 |
| Microfilm Bureau (North East) Limited(The) | Administrative & support | 1964 |
| Micromobility Partners Limited | Professional & scientific | 2022 |
| Middle East Shwarma (KD) Ltd | Hospitality | 2026 |
| Middleton Jewellery Repairs Ltd | Other services | 2014 |
| Mide African Food Store Limited | Wholesale & retail | 2025 |
| Miguel House of Fashion Limited | Wholesale & retail | 2025 |
| Mihai Claudiu Atanasiu Logistics Limited | Transport & logistics | 2025 |
| Mikbi Group Ltd | Professional & scientific | 2024 |
| Mikigami Ltd | Administrative & support | 2015 |
| Milan Pizza Grill Ltd | Hospitality | 2023 |
| Milanos Ryhope Ltd | Hospitality | 2016 |
| Milburn (NE) Limited | Hospitality | 2018 |
| Miles & Smiles Ltd | Wholesale & retail | 2025 |
| Miles Away Limited | Administrative & support | 2006 |
| Mill Hill Food Store Ltd | Wholesale & retail | 2026 |
| Millbanke Trading Ltd | Wholesale & retail | 2024 |
| Miller's Hospitality Ltd | Hospitality | 2025 |
| Millers the Bakers Ltd | Wholesale & retail | 2012 |
| Millford Financial Planning Limited | Financial services | 2013 |
| Million Chester Road Ltd | Wholesale & retail | 2024 |
| Million Healthcare Ltd | Wholesale & retail | 2023 |
| Million Medical Ltd | Wholesale & retail | 2013 |
| Million Millfield Ltd | Wholesale & retail | 2024 |
| Million Properties Ltd | Real estate | 2024 |
| Million ST Luke's Ltd | Wholesale & retail | 2024 |
| Millionaire Journey CIC | Education | 2022 |
| Milojo Ltd | Other services | 2018 |
| Miltons Bath Repair, Bath RE Enamelling & Bath Resurfacing Newcastle, Tyne & Wear Ltd | Other services | 2024 |
| Minchella's Roker Limited | Hospitality | 2021 |
| Minchella's Seaburn Limited | Hospitality | 2019 |
| Mindcat C. Limited | Administrative & support | 2025 |
| Mindfuljess Ltd | Information & communication | 2025 |
| Mindfulme Wellbeing Ltd | Other services | 2025 |
| Minerva Arts & Wellbeing | Education | 2017 |
| Minerva Consultancy Limited | Professional & scientific | 2026 |
| Minerva Training and Recruitment Limited | Education | 2023 |
| Minerva Training North East Community Interest Company | Education | 2024 |
| Ming Dynasty (Sunderland) Limited | Real estate | 1986 |
| Ming Garden Takeaway Ltd | Hospitality | 2022 |
| Minh Tung Ltd | Real estate | 2025 |
| Mini Amor Baby Wear Limited | Wholesale & retail | 2023 |
| Mini Mart Shop Ltd | Wholesale & retail | 2019 |
| Mini Miners Limited | Arts & recreation | 2019 |
| Mino Pizza Ltd | Hospitality | 2025 |
| Mint Management Entertainment Group Limited | Extraterritorial | 2011 |
| Mintel Communications Ltd | Wholesale & retail | 2020 |
| Minth Automotive (UK) Company Limited | Manufacturing | 2018 |
| Minth UK Holdings Limited | Financial services | 2024 |
| MIO Holding Limited | Professional & scientific | 2022 |
| Mircea Buildings Ltd | Construction | 2025 |
| Misand Taxis Ltd | Transport & logistics | 2024 |
| Miso Dining Ltd | Hospitality | 2025 |
| Miss Penguin PR Limited | Professional & scientific | 2012 |
| Mist Foods Ltd | Hospitality | 2025 |