| Mums CAN DO Ltd | Financial services | 2016 |
| MUN Group Ltd | Information & communication | 2026 |
| Munden Associates Limited | Real estate | 2012 |
| Munden Investments Ltd | Real estate | 2025 |
| Mundissimo Ltd | Construction | 2018 |
| Munroweb Limited | Information & communication | 2008 |
| Mura Trans-Uk Ltd | Transport & logistics | 2019 |
| Murala Investments Ltd | Real estate | 2023 |
| Murati Building Limited | Construction | 2023 |
| Murder One UK Limited | Wholesale & retail | 2009 |
| Mure Limited | Real estate | 2016 |
| Murphy Bros. Limited | Extraterritorial | 1945 |
| Murphy Geospatial UK Ltd | Professional & scientific | 2006 |
| Murphy Project Transformation Services Ltd | Professional & scientific | 2023 |
| Murva Limited | Information & communication | 2026 |
| Musa Brothers Fleet Ltd | Transport & logistics | 2023 |
| Musa's Farm Ltd | Manufacturing | 2020 |
| Muse Travel Ltd | Administrative & support | 2017 |
| Mushahid Medical Ltd | Health & social care | 2022 |
| Musica Universalis Organization Ltd | Education | 2021 |
| Musical Cocktails Limited | Administrative & support | 1997 |
| Muslim Mind CIC | Health & social care | 2025 |
| Mustachios Barbershop Ltd | Other services | 2019 |
| Mutebox Ltd | Wholesale & retail | 2023 |
| Muthr Ltd | Information & communication | 2026 |
| Muzo Limited | Health & social care | 2013 |
| MV Groceries Limited | Wholesale & retail | 2019 |
| MV701 Ltd | Wholesale & retail | 2025 |
| MVS Solutions Ltd | Information & communication | 2024 |
| MW Case Management Limited | Health & social care | 2022 |
| MW Consulting Solutions Limited | Administrative & support | 2016 |
| MW Testing Consultancy Limited | Professional & scientific | 2010 |
| MWA Health Ltd | Professional & scientific | 2013 |
| Mwamba Group Limited | Hospitality | 2025 |
| MWC Investments II Limited | Extraterritorial | 2018 |
| MWC Investments Limited | Administrative & support | 2014 |
| MWC Projects Ltd | Administrative & support | 2020 |
| MWM Solutions Limited | Professional & scientific | 2024 |
| MWR Limited | Professional & scientific | 2024 |
| Mwxyz Limited | Information & communication | 2020 |
| MX Subsea Ltd | Information & communication | 2014 |
| MX1402LTD Limited | Construction | 2024 |
| Mxvc Ltd | Real estate | 2019 |
| My 3 Chickens Limited | Hospitality | 2023 |
| My Beauty and Care Ltd | Manufacturing | 2013 |
| My Fashion Hub UK Ltd | Wholesale & retail | 2026 |
| My Financial Services Group Limited | Financial services | 2015 |
| My Gizzmo Limited | Wholesale & retail | 2021 |
| My Globel Ltd | Wholesale & retail | 2025 |
| My Instant Islamic Will Ltd | Other services | 2023 |
| My Life Counselling Practice Ltd | Health & social care | 2024 |
| My New Loft Limited | Construction | 2017 |
| My Pet Peeve Ltd | Information & communication | 2024 |
| My Treat Caddy Limited | Wholesale & retail | 2018 |
| My Trove Jewels Ltd | Wholesale & retail | 2025 |
| My Tuckers Limited | Administrative & support | 2015 |
| Mycarl Company Limited | Health & social care | 2022 |
| Mycology Research Laboratories Limited | Wholesale & retail | 1997 |
| Myelix Ltd | Information & communication | 2025 |
| Myers Clark Limited | Professional & scientific | 2010 |
| Myersglow Ltd | Health & social care | 2025 |
| Mykoka Misya Holdings Ltd | Financial services | 2021 |
| Mylo London Holding Limited | Financial services | 2023 |
| Mync Brands Limited | Wholesale & retail | 2012 |
| Myperfectred Ltd | Wholesale & retail | 2026 |
| Mypiazza Limited | Wholesale & retail | 2020 |
| Myprash Ltd | Administrative & support | 2016 |
| Myra Investments (UK) Ltd | Administrative & support | 2021 |
| Myrab Ltd | Health & social care | 2024 |
| Myriad POD Group Limited | Information & communication | 2024 |
| Myrtle Abode Ltd | Real estate | 2024 |
| Mysachcomms Limited | Professional & scientific | 2026 |
| Mysterious Code Ltd | Information & communication | 2014 |
| Mystic Meadow Ltd | Information & communication | 2010 |
| MYT Digital Ltd | Information & communication | 2021 |
| Myuksuites Limited | Real estate | 2018 |
| MZ Cloud Ltd | Information & communication | 2022 |
| MZ Fashion Fluent Ltd | Wholesale & retail | 2025 |
| MZ Pharmaceuticals Ltd | Other services | 2020 |
| MZM Decorating Ltd | Other services | 2016 |
| MZM Property Services Ltd | Other services | 2016 |
| N & Z Strategic Advisory Ltd | Financial services | 2026 |
| N and T Ferris Ltd | Real estate | 2014 |
| N B C (Watford) Ltd | Information & communication | 2003 |
| N Balam Consulting Limited | Professional & scientific | 2014 |
| N Clark Window Cleaning (Software) Limited | Administrative & support | 2016 |
| N Clark Window Cleaning Limited | Administrative & support | 2009 |
| N Coded Ltd | Professional & scientific | 2012 |
| N Hughes Building Contractors Limited | Construction | 2015 |
| N Miah Chai Ltd | Hospitality | 2025 |
| N S R Communications Limited | Manufacturing | 1994 |
| N W Barnett Properties Ltd | Real estate | 2019 |
| N&D Builders Ltd | Construction | 2018 |
| N&M Consultants Ltd | Professional & scientific | 2020 |
| N&M Housing Ltd | Real estate | 2019 |
| N&R Management Ltd | Real estate | 2025 |
| N-Vico Ltd | Construction | 2010 |
| N. Webb Electrotechnical Ltd | Construction | 2014 |
| N.A Homes Ltd | Real estate | 2020 |
| N.A.S Homes Ltd | Real estate | 2022 |