| Mama Jemimah's Kitchen Limited | Hospitality | 2021 |
| MAN Thats Handy Limited | Administrative & support | 2009 |
| Man-Tech Support Services Limited | Professional & scientific | 2014 |
| Manage the Future Limited | Extraterritorial | 2021 |
| Managed Print Partners Limited | Information & communication | 2013 |
| Management Consultancy Solutions Ltd | Administrative & support | 2015 |
| Manchester & Buxton Kart Club Limited | Arts & recreation | 1995 |
| Mane Inc Ltd | Other services | 2025 |
| Manija Limited | Hospitality | 2013 |
| Manjinder Kaur Limited | Administrative & support | 2023 |
| Mann Electrotechnical Ltd | Construction | 2024 |
| Manna Organic Ltd | Manufacturing | 2024 |
| Manners Farms Limited | Agriculture & fishing | 1957 |
| Manor Farm (Coulby Newham) Management Company Limited | Households | 2009 |
| Manq Properties Ltd | Real estate | 2024 |
| Manson Foods Limited | Wholesale & retail | 2018 |
| Maoni Business Solutions Limited | Professional & scientific | 2015 |
| MAP Building & Roofing Limited | Construction | 2018 |
| Maple & Twine Limited | Manufacturing | 2023 |
| MAR Delivery Limited | Transport & logistics | 2022 |
| Maratopia Digital Marketing Ltd | Professional & scientific | 2015 |
| Marc Properties Ltd | Construction | 2017 |
| Marcin Move Logistics Ltd | Transport & logistics | 2025 |
| Marcusdaisy Ltd | Administrative & support | 2016 |
| Marie Church Cognitive Behavioural Services Limited | Health & social care | 2017 |
| Marina Green Developments Limited | Professional & scientific | 2024 |
| Marinos Pizza N Ltd | Hospitality | 2020 |
| Marinos Pizzeria D Limited | Hospitality | 2026 |
| Mark Allatt Consulting Limited | Professional & scientific | 2001 |
| Mark Digger Limited | Construction | 2014 |
| Mark James Scott Boanson Ltd | Administrative & support | 2026 |
| Mark Lawrence Engineering Services Ltd | Construction | 2021 |
| Mark Pearse Ltd | Construction | 2002 |
| Markem Engineering Limited | Professional & scientific | 2011 |
| Marmoo Ltd | Information & communication | 2024 |
| Marple's Property Limited | Construction | 2025 |
| Marsden Damp Services Ltd | Construction | 2015 |
| Marshall & Associates' International Limited | Professional & scientific | 1997 |
| Marshall Property Rentals Limited | Real estate | 2012 |
| Marsland Languages Ltd | Education | 2016 |
| Marsons Transport Ltd | Transport & logistics | 2015 |
| Martin Building Ltd | Construction | 2015 |
| Martin Gray Football Academy Ltd | Arts & recreation | 2010 |
| Martin Healey Vehicle Adaptations Ltd | Wholesale & retail | 2014 |
| Martlesham Car Centre Ltd | Wholesale & retail | 2015 |
| Martyn Pease Property Company Limited | Real estate | 2024 |
| Mary Court (Jesmond) Limited | Households | 1997 |
| MAS Cash & Carry Ltd | Wholesale & retail | 2024 |
| Masala Art Limited | Hospitality | 2022 |
| Masala Spice Ltd | Hospitality | 2018 |
| Mascots Incorporated Ltd | Manufacturing | 2015 |
| Masons Truck & Plant Ltd | Administrative & support | 2018 |
| Massage Yoga Baby and ME Limited | Health & social care | 2010 |
| Master Order Limited | Administrative & support | 2023 |
| Masterhouse Roofing Ltd | Construction | 2017 |
| Masterhouse Services Ltd | Construction | 2016 |
| Masterlube Systems Limited | Professional & scientific | 1988 |
| Mathews & Mathews Limited | Health & social care | 2015 |
| Mathews&Philips Properties Limited | Real estate | 2024 |
| Matthew J Brown Limited | Construction | 2020 |
| Matthewsoobinko Ltd | Health & social care | 2019 |
| Maverick Deco Ltd | Manufacturing | 2025 |
| MAW Rope Access Services Ltd | Construction | 2023 |
| Mawers Holding Limited | Financial services | 2011 |
| Mawers Limited | Manufacturing | 1981 |
| Maxednewco Limited | Arts & recreation | 2026 |
| Maxwell Consultants Ltd | Information & communication | 2023 |
| Maxwell Stephens Ltd | Administrative & support | 1991 |
| Mayfield Owners (Darlington) Limited | Households | 1982 |
| Maze Engineering Consultants Limited | Professional & scientific | 2018 |
| MB Automation Solutions Ltd | Professional & scientific | 2024 |
| MB Events 2023 Limited | Extraterritorial | 2023 |
| MB Human Resources Consulting Ltd | Professional & scientific | 2012 |
| Mbe-Tec Ltd | Manufacturing | 2018 |
| MBR & RBG Limited | Construction | 2020 |
| Mbridges Medical Limited | Health & social care | 2023 |
| MC Ware IT Solutions Limited | Information & communication | 2013 |
| MCA Courier Ltd | Transport & logistics | 2022 |
| Mccote Ltd | Real estate | 2026 |
| MCE Engineering Services Limited | Manufacturing | 2018 |
| MCE Operations Management Ltd | Professional & scientific | 2025 |
| Mcfarlane H&S Consultants Limited | Professional & scientific | 2023 |
| Mcginley Construction Services Limited | Construction | 2018 |
| Mcgovern & Partners Limited | Information & communication | 2016 |
| MCL Group Holdings Limited | Financial services | 2023 |
| Mcmain Electrical Limited | Construction | 2009 |
| Mcmanus Property Teesside Ltd | Real estate | 2024 |
| Mcqueen Motors Ltd | Wholesale & retail | 2019 |
| MCS Joinery Ltd | Construction | 2018 |
| MCT Accountants Ltd | Professional & scientific | 2015 |
| MD Whiting Decorating Ltd | Construction | 2019 |
| MDC Design Limited | Professional & scientific | 2007 |
| MDE Interiors Ltd | Construction | 2015 |
| MDH Eco Properties Limited | Real estate | 2025 |
| MDL Instructor Leasing Ltd | Administrative & support | 2026 |
| MDL1 Ltd | Manufacturing | 2020 |
| MDS Joinery & Building Ltd | Construction | 2014 |
| Me&L Design Ltd | Professional & scientific | 2016 |
| ME3 Properties Ltd | Households | 2025 |
| Meadow Croft (Hipperholme) Management Company Limited | Households | 2012 |