| Merrivale Court Management Company Limited | Households | 2002 |
| Merrivale Energy Holdings Limited | Financial services | 2024 |
| Merrivale Farms Holdings Limited | Financial services | 2025 |
| Merrivale Farms Limited | Agriculture & fishing | 1979 |
| Merrix Works Ltd | Manufacturing | 2026 |
| Merrixgrogan Corporate Ltd | Financial services | 2012 |
| Merrixgrogan LLP | | 2009 |
| Merry Mary's Ltd | Hospitality | 2025 |
| Mersich MM S Ltd. | Health & social care | 2010 |
| Merstow Green Ltd | Extraterritorial | 2007 |
| Merus Court Management Company Limited | Construction | 2006 |
| Merysh Healthcare Services Ltd | Administrative & support | 2020 |
| Merysh Properties Ltd | Real estate | 2022 |
| Mesa Surveying Limited | Professional & scientific | 2025 |
| Mesh Cult Limited | Wholesale & retail | 2025 |
| Mesh Digital Limited | Information & communication | 2003 |
| Mesh Recruitment Ltd | Administrative & support | 2022 |
| Mesh Training Ltd | Information & communication | 2023 |
| Mess DOT Ltd | Hospitality | 2024 |
| Message PAD Limited | Administrative & support | 2023 |
| Messuages Investments (Nottm) Limited | | 1962 |
| Messy Ideas Art Ltd | Arts & recreation | 2026 |
| Messy Monsterz Limited | Education | 2015 |
| Messyhair Ltd | Wholesale & retail | 2019 |
| Mesywoods Ltd | Health & social care | 2019 |
| MET - Clad Contracts Limited | Construction | 1996 |
| Met-Clad Contracts (GB) Limited | Construction | 2023 |
| Met-Clad Contracts (UK) Limited | Administrative & support | 2000 |
| Met-Clad Contracts Group Limited | Professional & scientific | 2009 |
| Met-Clad Special Projects Limited | Construction | 2023 |
| Meta Associates Limited | Real estate | 2022 |
| Meta Construction Ltd | Construction | 2007 |
| Meta Origin Ltd | Financial services | 2020 |
| Meta Physical Ltd | Real estate | 2019 |
| Meta Procurement Ltd | Professional & scientific | 2022 |
| Metacbd Limited | Wholesale & retail | 2022 |
| Metafour Estates Ltd | Real estate | 2024 |
| Metal Garden Screen Ltd | Wholesale & retail | 2022 |
| Metal MAN Machines Ltd Limited | Manufacturing | 2025 |
| Metal Minds Limited | Extraterritorial | 2011 |
| Metal Process Services Holdings Limited | Manufacturing | 2018 |
| Metal Virtuosity Limited | Manufacturing | 2025 |
| Metal World Engineering Limited | Professional & scientific | 2009 |
| Metal World Holdings Limited | Financial services | 2015 |
| Metalduct (Nottingham) Limited | Manufacturing | 1998 |
| Metamaterials Ltd | Professional & scientific | 2021 |
| Metamorphic Additive Manufacturing Ltd | Professional & scientific | 2021 |
| Metamorphosis Children’S Homes Ltd | Health & social care | 2024 |
| Metatexxt Consultants Ltd | Professional & scientific | 2019 |
| Metatexxt Ltd | Extraterritorial | 2014 |
| Metcalf Contracts Properties Limited | Real estate | 2003 |
| Metcalfe Living Limited | Real estate | 2021 |
| Metcalfe Planning Services Limited | Professional & scientific | 2014 |
| Meteor Bidco Limited | Financial services | 2021 |
| Meteor Holdco Limited | Financial services | 2021 |
| Meteor Spares Services Ltd | Wholesale & retail | 2003 |
| Methodica Technologies Limited | Professional & scientific | 2020 |
| Methworth Limited | Professional & scientific | 1931 |
| Metis Clinical Limited | Professional & scientific | 2009 |
| Metis Company Limited | Real estate | 2023 |
| Metis International Advisory Ltd | Professional & scientific | 2024 |
| Metis Personal Wealth Advisors Limited | Financial services | 2018 |
| Metlab Industrial Limited | Water & waste | 2016 |
| Metlane Lettings Limited | Real estate | 2006 |
| Metool Products Limited | Manufacturing | 1941 |
| Metric Bidco Limited | Administrative & support | 2024 |
| Metric Imperial Bolt Limited | Manufacturing | 2014 |
| Metric Search Holdings Limited | Administrative & support | 2022 |
| Metric Search Limited | Administrative & support | 2020 |
| Metric Topco Limited | Administrative & support | 2024 |
| Metrichouse Ltd | Information & communication | 2026 |
| Metriq Consulting Limited | Information & communication | 2025 |
| Metriscope Ltd | Information & communication | 2021 |
| Metro GB Limited | Wholesale & retail | 2009 |
| Metro Housing Management Limited | Other services | 2023 |
| Metro Orchard Limited | Information & communication | 2025 |
| Metro Vista LAB Limited | Information & communication | 2025 |
| Metron Advanced Equipment Limited | Professional & scientific | 2009 |
| Metron I P Limited | Administrative & support | 2016 |
| Metsi Bidco Limited | Financial services | 2023 |
| Metsi Group Limited | Information & communication | 2017 |
| Metsi Midco 1 Limited | Financial services | 2023 |
| Metsi Midco 2 Limited | Financial services | 2023 |
| Metsi Topco Limited | Financial services | 2023 |
| Mevell House Management Limited | Households | 1993 |
| MEW Electrical Contractor Ltd | Construction | 2021 |
| MEW Transport Ltd | Transport & logistics | 2025 |
| Mewar Haveli Northampton Ltd | Hospitality | 2021 |
| Mexh Andreas Ltd | Wholesale & retail | 2020 |
| Meyah Group Services Limited | Professional & scientific | 2024 |
| Meybo U.K (Distribution) Limited | Extraterritorial | 2011 |
| Mezgo Mini Market Limited | Wholesale & retail | 2025 |
| Mezza Turkish Cuisine Limited | Hospitality | 2025 |
| MF Consultants Ltd | Professional & scientific | 2018 |
| MF Gaming Limited | Administrative & support | 2011 |
| MF Group Holdings Ltd | Professional & scientific | 2015 |
| MF Lighting and Testing Limited | Construction | 2023 |
| MF Safety Ltd | Wholesale & retail | 2026 |
| MFG UK Limited | Information & communication | 2008 |
| MFK Express Limited | Real estate | 2020 |