| Maclaren Investments Limited | Financial services | 2025 |
| Macol Holding Limited | Extraterritorial | 2021 |
| Macol Limited | Wholesale & retail | 1980 |
| MAD Party Ltd | Wholesale & retail | 2025 |
| MAD4 Business Ltd | Professional & scientific | 2020 |
| Made Easier Limited | Manufacturing | 2023 |
| Madhani Ltd | Real estate | 2017 |
| Madras Kitchen Ltd | Real estate | 2019 |
| MAF Civil Engineering Ltd | Construction | 2024 |
| MAG Martin Ltd | Wholesale & retail | 2020 |
| Magi Enterprises UK Limited | Wholesale & retail | 2015 |
| Magi Retail UK Limited | Wholesale & retail | 2025 |
| Magic Faraway Tree Limited | Hospitality | 2025 |
| Magic International Limited | Manufacturing | 1998 |
| Magic Triple Seven Cleaning Ltd | Administrative & support | 2024 |
| Maginot Properties Limited | Construction | 2006 |
| Magnus Creative Limited | Real estate | 1973 |
| MAH Advisory Limited | Professional & scientific | 2026 |
| Mahakala Systems Ltd | Information & communication | 2019 |
| Mahalisounds Ltd | Hospitality | 2024 |
| Mahaprasad Limited | Manufacturing | 2018 |
| Maharsh Automobiles Ltd | Wholesale & retail | 2025 |
| Mahaveer Microventures Ltd | Real estate | 2025 |
| Mahendra Overseas Limited | Wholesale & retail | 2007 |
| Mahesha Software Solutions Ltd | Information & communication | 2019 |
| Mahir Fire Protection Limited | Other services | 2017 |
| Mahir Property Investments Limited | Real estate | 2026 |
| Mahre Limited | Real estate | 2025 |
| Maianne Limited | Construction | 2017 |
| Mainline Estates Limited | Other services | 2017 |
| Maison Arabi Ltd | Wholesale & retail | 2023 |
| Maison Dieu Limited | Real estate | 2018 |
| Maison Dieu Properties Limited | Real estate | 2018 |
| Maison Hotelier Limited | Wholesale & retail | 2019 |
| MAJ Construction (London) Limited | Construction | 2016 |
| Majestic Clinic Limited | Health & social care | 2021 |
| Majithia & Bhere Group Limited | Real estate | 2025 |
| Major Constructions Ltd | Construction | 2017 |
| Majortown Limited | Real estate | 2001 |
| Majreha Ltd | Professional & scientific | 2024 |
| Maka Skincare Limited | Health & social care | 2024 |
| Makav Ltd | Financial services | 2024 |
| Make That Change Consulting Ltd | Professional & scientific | 2019 |
| Makeva Ltd | Manufacturing | 2025 |
| Makwana Solicitors Limited | Professional & scientific | 2018 |
| Malachite Events Limited | Professional & scientific | 2024 |
| Malachy Molloy Associates Ltd | Information & communication | 2002 |
| Malaika Investments 2 Limited | Financial services | 2015 |
| Malaika Investments Limited | Real estate | 2014 |
| Malci Construction Limited | Construction | 2017 |
| Maldon Ltd | Real estate | 2019 |
| Malhaar Food Ltd | Hospitality | 2025 |
| Malibu (Trademarks) Ltd | Other services | 2005 |
| Malibu Club Limited | Real estate | 2000 |
| Malik CAB Ltd | Transport & logistics | 2024 |
| Mall Engineering Services Ltd | Professional & scientific | 2024 |
| Malny CHA Limited | Hospitality | 2018 |
| Mamba Enterprises Limited | Wholesale & retail | 1991 |
| Mamushroom Ltd | Hospitality | 2025 |
| Management Consulting Ltd | Administrative & support | 2016 |
| Management Information Systems & Technologies Limited | Construction | 1997 |
| Manamanx Limited | Wholesale & retail | 2024 |
| Manas Labs Ltd | Information & communication | 2026 |
| Manchester Square Properties Limited | Construction | 1989 |
| Manee House Limited | Other services | 2017 |
| Manefit Ladies Gym Ltd | Arts & recreation | 2025 |
| Maneph Resources Limited | Wholesale & retail | 2005 |
| Mangal Property Limited | Real estate | 2022 |
| Mangan Limited | Professional & scientific | 2025 |
| Manhome Management Ltd | Real estate | 2025 |
| Manik 360 Limited | Information & communication | 2017 |
| Manmittang Limited | Health & social care | 2024 |
| Manor Capital LLP | | 2010 |
| Manor House 46 London Road Blackwater Management Company Limited | Extraterritorial | 2015 |
| Manow Wealth Partners Ltd | Financial services | 2023 |
| Manxcharm Limited | Construction | 1980 |
| Mapesbury Securities Limited | Administrative & support | 2023 |
| Maple Leaf Buildings Limited | Real estate | 2015 |
| Marbi Transport Ltd | Transport & logistics | 2024 |
| Marc Investments Stanmore Limited | Real estate | 2010 |
| Marcole Limited | Administrative & support | 2003 |
| Marcwood Limited | Construction | 1993 |
| Mardon Residents Management Limited | Real estate | 1967 |
| Marengo Construction Ltd | Construction | 2018 |
| Marengo Developments Limited | Construction | 2025 |
| Marengo Group Ltd | Financial services | 2025 |
| Margarets Court Freehold Limited | Households | 2012 |
| Margarets Court RTM Company Limited | Households | 2011 |
| Margot RB Consulting Limited | Professional & scientific | 2017 |
| Marho Investments Ltd | Wholesale & retail | 2021 |
| Mari Estates Ltd | Real estate | 2026 |
| Mariano FURNITURE90 Ltd | Construction | 2022 |
| Marina Tokar Brand Strategy Limited | Professional & scientific | 2021 |
| Marine Road Real Estate Ltd | Real estate | 2020 |
| Mariosal Ltd | Transport & logistics | 2024 |
| Mark Flynn Plumbing Limited | Construction | 2003 |
| Mark Naber Consulting Limited | Other services | 2004 |
| Mark Sasta & Associates Limited | Professional & scientific | 2021 |
| Market Alcohol 24/7 Limited | Wholesale & retail | 2025 |
| Market Garden Homes Limited | Construction | 2023 |