| Mergulo Ltd | Manufacturing | 2019 |
| Messam & Rider Limited | Professional & scientific | 1998 |
| Messerschmitt Owners' Club Limited | Other services | 2005 |
| Messybeanz Ltd | Health & social care | 2024 |
| Metadataworks Limited | Information & communication | 2017 |
| Metavate Limited | Wholesale & retail | 2009 |
| Metric Central Ltd | Information & communication | 2019 |
| Metropolitan & Scott Limited | Professional & scientific | 2009 |
| MEX Consultants Ltd | Professional & scientific | 2024 |
| Mexicanosss Limited | Hospitality | 2024 |
| MF Sweden Limited | Information & communication | 2024 |
| MFM Project UK CIC | Education | 2014 |
| Mgcad Limited | Professional & scientific | 2004 |
| MGQ Consulting Limited | Professional & scientific | 2025 |
| MH Business Intelligence Ltd | Information & communication | 2022 |
| MI Home Investments Ltd | Real estate | 2018 |
| MIA Surgical Services Ltd | Health & social care | 2024 |
| Miaem Limited | Wholesale & retail | 2025 |
| Miami Avalon Ltd | Information & communication | 2022 |
| Mickleton Antique Centre Limited | Wholesale & retail | 2020 |
| Micro Property Limited | Real estate | 2019 |
| Microboards Technology Limited | Information & communication | 1997 |
| MID Warwickshire Yacht Club Ltd | Arts & recreation | 2022 |
| Midas Touch Ltd | Wholesale & retail | 2025 |
| Middlemarch Business Park Management Limited | Real estate | 2001 |
| Midland Asbestos Survery Services Limited | Professional & scientific | 2026 |
| Midland Assured Assets Limited | Real estate | 2016 |
| Midland Assured Consulting Limited | Real estate | 2008 |
| Midland Assured Developments LLP | | 2009 |
| Midland Assured Estates Limited | Real estate | 1954 |
| Midland Assured Finance Limited | Financial services | 1963 |
| Midland Assured Holdings Limited | Professional & scientific | 2005 |
| Midland Assured Homes (1990) Limited | Real estate | 1989 |
| Midland Assured Homes Limited | Real estate | 1989 |
| Midland Mortgage Services Limited | Financial services | 2005 |
| Midland Quality Control Ltd | Professional & scientific | 2024 |
| Midlands BAT Surveys Limited | Professional & scientific | 2026 |
| Midlands Property Consultancy Ltd | Professional & scientific | 2022 |
| Midlands Reclamation and Waste Limited | Water & waste | 2002 |
| Midshires Estates Limited | Construction | 1990 |
| Midwinters Vineyard Ltd | Agriculture & fishing | 2024 |
| Miglo Limited | Wholesale & retail | 2026 |
| Mihaleya Ltd | Wholesale & retail | 2023 |
| Mike Nevin Consulting Limited | Administrative & support | 2002 |
| Milkbar Deli Company Limited | Hospitality | 2026 |
| Mill Street Consultants LLP | | 2004 |
| Millpark Solutions Ltd | Extraterritorial | 2026 |
| Mills Venue Consulting Ltd | Hospitality | 2022 |
| Milltroy Services Ltd | Wholesale & retail | 2026 |
| Millwood King & Co Limited | Real estate | 2026 |
| Milton Keynes Autorama Limited | Wholesale & retail | 1985 |
| Milverton Crescent Management Company Limited | Households | 2015 |
| Minas Medical Services Ltd | Health & social care | 2024 |
| Mindful Pilates Studio Ltd | Arts & recreation | 2021 |
| Minibus Rides Ltd | Transport & logistics | 2024 |
| Minoan Design & Manufacture Limited | Manufacturing | 2025 |
| Mint Residential Solutions Limited | Real estate | 2020 |
| MIO Dolce Ltd | Hospitality | 2024 |
| Mioperation Ltd | Information & communication | 2021 |
| Mirador Solutions Ltd | Information & communication | 2005 |
| Miscellaneous Bannings Ltd | Other services | 2018 |
| Mistral House Hinckley 2025 Limited | Real estate | 2025 |
| Misundrstd Ltd | Manufacturing | 2025 |
| Mixmove Limited | Information & communication | 2020 |
| MJC Construction (Midlands) Ltd | Construction | 2018 |
| MK Midlands Limited | Hospitality | 2026 |
| MK Realty Group Ltd | Real estate | 2024 |
| MK Vehicles & Arts Ltd | Wholesale & retail | 2018 |
| MKJ Brahma Property Investments Ltd | Real estate | 2022 |
| Mlolongo 1 (UK) Ltd | Construction | 2022 |
| MLS Engineering Consultancy Ltd | Professional & scientific | 2025 |
| MMB Property Holdings Limited | Financial services | 2026 |
| Mobile Fluid Limited | Wholesale & retail | 2014 |
| Mobunti Limited | Information & communication | 1994 |
| Mocassar (Investment) Limited | Professional & scientific | 1976 |
| Modern Glazing Limited | Other services | 2020 |
| Modern Patterns Ltd | Information & communication | 2025 |
| Modern Property Ltd | Real estate | 2019 |
| Modular Retreats Limited | Construction | 2021 |
| Mohawk’S UK Limited | Wholesale & retail | 2026 |
| Mojo Racing Engines Limited | Professional & scientific | 2023 |
| Mojo Well-Being and Resilience Specialist Ltd | Public administration | 2020 |
| Mokesa UK Limited | Manufacturing | 2024 |
| Molly Olly's Wishes | Professional & scientific | 2011 |
| Molyneux Momentum Limited | Professional & scientific | 2025 |
| MON LOT Ltd | Health & social care | 2024 |
| Monarch Equity Limited | Real estate | 2020 |
| Monecko Ltd | Wholesale & retail | 2020 |
| Money Concepts Limited | Financial services | 2002 |
| Money Shield Ltd | Other services | 2018 |
| Mongewell Limited | Agriculture & fishing | 1992 |
| Monitor ERP System UK Ltd | Information & communication | 2025 |
| Mono Food Ltd | Hospitality | 2026 |
| Montague Storage Limited | Administrative & support | 2005 |
| Montgomery Avenue Residents' Association Limited | Real estate | 1995 |
| Moolec Science Limited | Professional & scientific | 2020 |
| Moon & Back Assets Limited | Professional & scientific | 2026 |
| Moondesk Limited | Financial services | 2023 |
| Moore & Tibbits Limited | Administrative & support | 2011 |
| Moore Capital Ltd | Real estate | 2015 |