| MAK Agricultural Ltd | Financial services | 2015 |
| Malabari Ltd | Hospitality | 2024 |
| Maltby Overseas Property Consultants Limited | Real estate | 2006 |
| Mama's Pizzeria Limited | Hospitality | 2018 |
| Mama's Takeaway 2025 Ltd | Hospitality | 2025 |
| Mameen Consultancy Ltd | Information & communication | 2025 |
| Mamta Labs Ltd | Wholesale & retail | 2025 |
| Mamta Properties (NE) Ltd | Construction | 2025 |
| Mamxiety Ltd | Wholesale & retail | 2022 |
| Mamxiety Play Cafe Ltd | Hospitality | 2025 |
| Manage-Safety Limited | Extraterritorial | 2025 |
| Management Operations Limited | Construction | 2019 |
| Mandale Property Group Ltd | Construction | 2020 |
| Manders Group Limited | Financial services | 2020 |
| Manders Property Developments Ltd | Real estate | 2020 |
| Mandour Group Ltd | Professional & scientific | 2021 |
| Mangai Limited | Wholesale & retail | 2022 |
| Mangos Property Group Ltd | Real estate | 2024 |
| Manilla Public Relations Ltd | Professional & scientific | 2013 |
| Manish Tyres Ltd | Manufacturing | 2025 |
| Manix Logistics Limited | Transport & logistics | 2026 |
| Mannequin Cafe C.I.C. | Wholesale & retail | 2013 |
| Mannimai Ltd | Other services | 2025 |
| Manolia Properties Limited | Real estate | 2024 |
| Manor Close Investments Limited | Real estate | 2012 |
| Manor Grange Construction Limited | Construction | 2017 |
| Manor Investments (NE) Limited | Real estate | 2024 |
| Mansfield Furniture Ltd | Manufacturing | 2020 |
| Mansion Vantage Limited | Administrative & support | 2024 |
| Manta Management Ltd | Construction | 2020 |
| Manta Studio Ltd | Information & communication | 2025 |
| MAP NDT Inspection Services Limited | Professional & scientific | 2015 |
| Maple Leaf (Education Sales) Ltd | Wholesale & retail | 2021 |
| Maranzo Ltd | Transport & logistics | 2013 |
| Marble Holdings Group Ltd | Real estate | 2026 |
| Marc Norton Ltd | Professional & scientific | 2017 |
| Marcaw Ltd | Hospitality | 2024 |
| Marco Inspection Limited | Professional & scientific | 2017 |
| Mardec Utilities Limited | Construction | 2015 |
| Mardi Gras Leisure Limited | Hospitality | 2025 |
| Marelektek Limited | Energy | 2018 |
| Margita Brickwork Ltd | Manufacturing | 2025 |
| Margot Online Limited | Wholesale & retail | 2026 |
| Margot-Kelly Limited | Wholesale & retail | 2025 |
| Marian Construction Limited | Construction | 2019 |
| Mariana Decoration & Designers Ltd | Professional & scientific | 2020 |
| Marinecrown Limited | Construction | 1980 |
| Marinos Eston Pizzeria Ltd | Hospitality | 2026 |
| Marinsharya Ltd | Professional & scientific | 2023 |
| Mark Hall Engineering Ltd | Professional & scientific | 2013 |
| Mark Johnston Engineering Services North East Limited | Professional & scientific | 2014 |
| Mark Mckenzie Decorating Services Ltd | Construction | 2026 |
| Mark Roberts Engineering Limited | Professional & scientific | 2017 |
| MARKETING4THETRADE Ltd | Professional & scientific | 2025 |
| Markley Ltd | Professional & scientific | 2024 |
| Markyns Limited | Health & social care | 2023 |
| Marland Used Furniture Ltd | Other services | 2025 |
| Marley Peter Limited | Wholesale & retail | 2025 |
| Marlwood Property Management Limited | Real estate | 2020 |
| Maroliz Technologies Limited | Administrative & support | 2017 |
| Marsh Property Group Limited | Real estate | 2023 |
| Marshall Jakeman Marine Ltd | Professional & scientific | 2019 |
| Marshalls Waste Services Ltd | Water & waste | 2024 |
| Marshbrook Motors Limited | Wholesale & retail | 2010 |
| Marshstone Motor Company Ltd | Wholesale & retail | 2026 |
| Marske Car Sales Ltd | Wholesale & retail | 2015 |
| Marske Investments Ltd | Hospitality | 2019 |
| Marston Construction and Shutdowns Limited | Professional & scientific | 2025 |
| Marston Green Practice Limited | Health & social care | 2018 |
| Marston Offshore Services Ltd | Manufacturing | 2026 |
| Martin & Sons Garage Ltd | Wholesale & retail | 2025 |
| Martin Delivery Service Ltd | Transport & logistics | 2026 |
| Marton Barbers Ltd | Other services | 2025 |
| Marton Bistro Limited | Hospitality | 2019 |
| Marton Brownfield Services Limited | Professional & scientific | 2006 |
| Marton Cricket Club (Community) Limited | Hospitality | 2019 |
| Marton Cricket Club Limited | Arts & recreation | 2019 |
| Marton Engineering Services Ltd. | Construction | 2017 |
| Marton Properties Limited | Real estate | 2022 |
| Marton Road Auto Centre Ltd | Wholesale & retail | 2023 |
| Marton Road Car Sales Ltd | Wholesale & retail | 2011 |
| Marton Road MOT Centre Ltd | Wholesale & retail | 2023 |
| Marvel Tech Limited | Wholesale & retail | 2024 |
| Marwa's Investment Ltd | Real estate | 2026 |
| Marymo Ltd | Wholesale & retail | 2017 |
| MAS & B Services Limited | Transport & logistics | 2023 |
| MAS Body Development Limited | Wholesale & retail | 2011 |
| MAS Body Health & Fitness Limited | Arts & recreation | 2017 |
| MAS Structures Limited | Professional & scientific | 2024 |
| Mase Solutions Limited | Manufacturing | 2023 |
| Mash Property Management Ltd | Construction | 2024 |
| Mashia Group Ltd | Wholesale & retail | 2026 |
| Mason & Co Stokesley Limited | Wholesale & retail | 2024 |
| Mason Capital Investments Ltd | Financial services | 2015 |
| Mason Rigging and Lifting Solutions Limited | Professional & scientific | 2022 |
| Masonic Hall (Middlesbrough) Limited | Health & social care | 1951 |
| Mass Vapour Ltd | Wholesale & retail | 2015 |
| Massala Ltd | Hospitality | 2019 |
| Massey Applied Solutions Ltd | Construction | 2023 |
| Massive Asif Limited | Arts & recreation | 2023 |