| Micmac Travel Limited | Hospitality | 1994 |
| Microscopix Limited | Wholesale & retail | 2000 |
| Middlebrook Nazeing Limited | Construction | 2026 |
| Middleclover (Swindon) Management Company Limited | Households | 2007 |
| Mike Prosser Limited | Professional & scientific | 2012 |
| Milazzo Properties Limited | Construction | 2015 |
| Milestone Masonry Ltd | Construction | 1983 |
| Mill Chase (Alverthorpe Road, NO. 2) Management Company Limited | Households | 2002 |
| Mill Green (Warton) Management Company Limited | Households | 2021 |
| Mill Parc (NO.2) Management Company Limited | Households | 2002 |
| Miller (Merton) Management Company Limited | Households | 1986 |
| Miller Brook Management Company Limited | Households | 2003 |
| Miller Point Management Company Limited | Households | 2011 |
| Millstone Walk Residents Management Company Limited | Households | 2025 |
| MIM Builders & Electrical Suppliers Ltd | Administrative & support | 2020 |
| Mind Performance Specialist Limited | Administrative & support | 2026 |
| Mindcare Consultancy Limited | Health & social care | 2015 |
| Mindful Pictures Ltd | Information & communication | 2020 |
| Mint Services Ltd | Administrative & support | 2022 |
| Mint-Print Properties Limited | Construction | 1985 |
| Mirabela Ltd | Wholesale & retail | 2016 |
| MIS Support Ltd | Information & communication | 2010 |
| Misiu Service Ltd | Wholesale & retail | 2018 |
| Misl Ssird Data Technology Ltd | Extraterritorial | 2015 |
| Miss Bright UK Ltd | Administrative & support | 2023 |
| Mitr Restaurant Ltd | Hospitality | 2024 |
| MJ. Gallagher Construction Limited | Construction | 2024 |
| Mjwrbarber Ltd | Other services | 2023 |
| MK Cleaning & Maintenance Limited | Administrative & support | 2012 |
| MM Wholesalers Ltd | Wholesale & retail | 2019 |
| MMJ London Limited | Manufacturing | 2012 |
| Monaveen House Management Company Limited | Households | 2018 |
| Monks Wood Management Company Limited | Households | 2004 |
| Montessori Property Holdings Limited | Real estate | 2021 |
| Montfort Place (Odiham) Management Company Limited | Households | 2014 |
| Moor Lane (Preston) Management Company Limited | Households | 2006 |
| Moorcraft Limited | Other services | 2018 |
| Moore Effects Ltd | Real estate | 2021 |
| Moore Teachers Ltd | Education | 2012 |
| Moorfield Park Management Company Limited | Households | 2018 |
| Moorgate Boulevard (Apartments) Management Company Limited | Households | 2022 |
| Moorlands Cleckheaton Management Company Limited | Households | 2018 |
| Moovin Consultancy Services Limited | Professional & scientific | 2019 |
| MOR OR LES Productions Limited | Information & communication | 2014 |
| Mora Consult Limited | Professional & scientific | 2021 |
| More Than Just a Cleaner Ltd | Administrative & support | 2024 |
| More Than Just an Organiser Ltd | Professional & scientific | 2026 |
| Moreton Dairy London Ltd | Wholesale & retail | 2020 |
| Moreton Rise (Bury ST Edmunds) Management Company Limited | Households | 2006 |
| Morgan Court Residents Association Limited | Extraterritorial | 2004 |
| Morgenwonen Limited | Construction | 1977 |
| Morph Plastering Limited | Construction | 2025 |
| Morreale Investment Ltd | Real estate | 2021 |
| Moth Flooring Limited | Other services | 2007 |
| Moulage Ltd | Extraterritorial | 2016 |
| Moule Property Limited | Real estate | 2021 |
| Mount Pleasant (Hatfield) Management Company Limited | Households | 2013 |
| Mowers Imports Limited | Administrative & support | 2010 |
| Moyler Investments LLP | | 2017 |
| Moyler Properties Limited | Real estate | 2021 |
| MP Executive Cars Limited | Transport & logistics | 2025 |
| MP Print Limited | Manufacturing | 2023 |
| MP Taxis & Executive Cars Limited | Transport & logistics | 2019 |
| MPC Construction London Ltd | Construction | 2017 |
| MR Baker's Cakes Limited | Hospitality | 2022 |
| MR Blue 88 Ltd | Wholesale & retail | 2026 |
| MR Marvel Magic Limited | Arts & recreation | 2009 |
| MR Marvel Parties Limited | Extraterritorial | 2009 |
| MR Stays Ltd | Real estate | 2025 |
| MR Unique Ltd | Wholesale & retail | 2023 |
| Mriah Limited | Wholesale & retail | 2008 |
| Mrmilk Ltd | Wholesale & retail | 2022 |
| MRX Technical Ltd | Arts & recreation | 2026 |
| MSC Bathrooms Ltd | Construction | 2013 |
| MT Medical Services Limited | Health & social care | 2021 |
| MTC Vision Limited | Administrative & support | 2023 |
| Mucky Madness Limited | Education | 2017 |
| Mulberry Gardens (Hamilton) Management Company Limited | Households | 2006 |
| Mulberry Park Estate Management Company Limited | Households | 2014 |
| Mulberry Place (Whitchurch) Management Company Limited | Households | 2001 |
| Multi Premium Sprayers Ltd | Manufacturing | 2023 |
| Muniverse Limited | Education | 2016 |
| Munsy Limited | Professional & scientific | 2017 |
| Murray Maintenance Ltd | Construction | 2026 |
| Muson & Hills LLP | | 2011 |
| Muson Apaberg Limited | Professional & scientific | 2011 |
| MW Executive Cars Ltd | Administrative & support | 2021 |
| MW Management & PR Ltd | Professional & scientific | 2018 |
| MW Metals Limited | Wholesale & retail | 2021 |
| My Coffee Machine Limited | Wholesale & retail | 2025 |
| My Wellbeing IQ Ltd | Wholesale & retail | 2019 |
| My World Therapy Ltd | Health & social care | 2021 |
| Myddleton Gate (Islington) Management Co. Limited | Households | 1995 |
| Mysa Kitchen Ltd | Hospitality | 2026 |
| N M Building and Roofing Ltd | Administrative & support | 2019 |
| N&D Herts Building Solutions Ltd | Construction | 2026 |
| N.D. Aquatics Limited | Manufacturing | 2006 |
| Naden Mill Management Company Limited | Households | 2006 |
| Nailicious Beauty Ltd | Other services | 2014 |
| Nala Investments Ltd | Real estate | 2021 |