| M&A Fitness Ltd | Arts & recreation | 2023 |
| M&B Consultants Ltd. | Wholesale & retail | 2018 |
| M&S Express Ltd | Other services | 2020 |
| M. Wass Building and Maintenance Ltd | Construction | 2022 |
| M.A.C. Developments & Construction Limited | Construction | 1989 |
| M.A.O. Electrical (UK) Limited | Construction | 2003 |
| M.E. Wilkinson Limited | Manufacturing | 1983 |
| M.J Engineering Solutions Ltd | Manufacturing | 2012 |
| M.J.Greatrex Limited | Construction | 1965 |
| M@K ITE Ltd | Information & communication | 2025 |
| MAC Projects (Bosworth) Limited | Manufacturing | 2017 |
| MAC Properties Management Limited | Real estate | 2022 |
| Machinery World Holdings Limited | Financial services | 2004 |
| Machinery World Limited | Wholesale & retail | 2000 |
| Mackenzie CAD Designs Ltd | Professional & scientific | 2014 |
| Macktek Dynamics Ltd | Professional & scientific | 2024 |
| Macmay Transport Ltd | Transport & logistics | 2021 |
| Maco Transport Ltd | Transport & logistics | 2018 |
| Macoana Ltd | Administrative & support | 2017 |
| Macy's Lifestyle Ltd | Manufacturing | 2024 |
| MAD Goose Design Limited | Administrative & support | 2012 |
| Madbug Preconstruction Services Limited | Professional & scientific | 2024 |
| Maddy's Limited | Hospitality | 2014 |
| Madina Halal Meat & Grocery Ltd | Wholesale & retail | 2024 |
| Mado Mini Market Ltd | Wholesale & retail | 2025 |
| Mafresh Limited | Health & social care | 2022 |
| MAG Premium Ltd | Construction | 2023 |
| Mag-Refinishes Ltd | Wholesale & retail | 2026 |
| Magic Flavours Limited | Hospitality | 2023 |
| Magicgloves Ltd | Administrative & support | 2025 |
| Magna Display Systems Limited | Manufacturing | 1998 |
| Magna Parva Limited | Information & communication | 2005 |
| Magna Produce Ltd | Wholesale & retail | 2019 |
| Magna SET Building Limited | Construction | 2016 |
| Magna Signs Limited | Manufacturing | 2013 |
| Magpie Event Production Ltd | Arts & recreation | 2023 |
| Magrito Ltd | Hospitality | 2024 |
| Mahon-Fleming Limited | Construction | 2003 |
| Mahuk Ltd | Wholesale & retail | 2022 |
| MAID2CLEAN (South East London) Ltd | Administrative & support | 2012 |
| MAID2CLEAN East Midlands Ltd | Administrative & support | 2012 |
| MAID2CLEAN Edinburgh Ltd | Administrative & support | 2012 |
| MAID2CLEAN ELS Ltd | Administrative & support | 2021 |
| MAID2CLEAN North Devon Ltd | Administrative & support | 2022 |
| Maintain Your Cool Limited | Administrative & support | 2013 |
| Majha Block Local Ltd | Wholesale & retail | 2024 |
| Make IT Creative Ltd | Professional & scientific | 2019 |
| Makemyhair Salon Limited | Other services | 2025 |
| Malayali Kada Limited | Wholesale & retail | 2023 |
| Malham Investments Limited | Real estate | 2024 |
| Malin Corporation Limited | Extraterritorial | 2023 |
| Malt Shovel (Hartshill) Ltd | Hospitality | 2015 |
| Mama Property Ltd | Real estate | 2024 |
| Mama’S Little Bakehouse Ltd | Wholesale & retail | 2024 |
| Mamsa Property Ltd | Real estate | 2023 |
| MAN Autoparts Ltd | Wholesale & retail | 2023 |
| Manding Entertainment Limited | Arts & recreation | 2018 |
| Manic Trade Services Ltd | Administrative & support | 2018 |
| Manor Building Services Limited | Extraterritorial | 2019 |
| Manor Court Chambers (Holdings) Limited | Administrative & support | 2022 |
| Manor Court Chambers Limited | Real estate | 2013 |
| Manor House Property Investments Limited | Real estate | 2026 |
| Manor Mews Weddings Ltd | Hospitality | 2022 |
| Mansan Building Services Ltd. | Construction | 2015 |
| MANU1990 Ltd | Transport & logistics | 2018 |
| Manzarai Clinic Limited | Health & social care | 2025 |
| Manzoor Traders Ltd | Wholesale & retail | 2025 |
| Mapledawn Limited | Construction | 2020 |
| MAR Commercial (South) Ltd | Real estate | 2023 |
| Maraga Ltd | Wholesale & retail | 2018 |
| Marbe Transport Ltd | Transport & logistics | 2020 |
| Marc Catry Limited | Wholesale & retail | 2019 |
| Marcel Ciorita Ltd | Transport & logistics | 2025 |
| Marcin Fire Limited | Construction | 2021 |
| Marco Paul Logistic Ltd | Transport & logistics | 2015 |
| Marco Transport Ltd | Transport & logistics | 2016 |
| Marco's Pizza Pasta Kebab Limited | Hospitality | 2024 |
| Marcri Trans Ltd | Transport & logistics | 2021 |
| Marcus Grindley Ltd | Construction | 2018 |
| Margarito Pizza & BBQ Ltd | Hospitality | 2026 |
| Mari Insulation Solution Ltd | Construction | 2023 |
| Maria Area Limited | Transport & logistics | 2026 |
| Marian Cretu Ltd | Transport & logistics | 2015 |
| Marina's House Ltd | Wholesale & retail | 2023 |
| Mario DRIVE4YOU Ltd | Transport & logistics | 2017 |
| Mario James Precision Engineering Limited | Professional & scientific | 2022 |
| Marioara INT Transport Ltd | Transport & logistics | 2025 |
| Mariusz Dryla Ltd | Administrative & support | 2014 |
| Marjorie ANN Investments Limited | Real estate | 2012 |
| Mark Blair Mortgage & Finance Limited | Financial services | 2009 |
| Mark Bugg Limited | Information & communication | 2007 |
| Mark Laurence Estate Agents Limited | Real estate | 2002 |
| Mark Machine Tools Ltd | Manufacturing | 2015 |
| Mark Sutton Builders Ltd | Construction | 2007 |
| Marked Holdings Limited | Financial services | 2025 |
| Market Bosworth CIC | Administrative & support | 2016 |
| Market Bosworth Consultants Ltd | Professional & scientific | 2014 |
| Market Bosworth Festival Limited | Arts & recreation | 2004 |
| Marlej Ltd | Transport & logistics | 2022 |
| Marner Ltd | Real estate | 2024 |