| Mobile Car Care Limited | Wholesale & retail | 2025 |
| Mobile Mammography Ltd | Health & social care | 2020 |
| Mobile Paradigm Consultancy Limited | Information & communication | 2014 |
| Mobile Street Limited | Wholesale & retail | 2009 |
| Mobile TEK8 Limited | Other services | 2017 |
| Mobileyes Software Ltd | Information & communication | 2008 |
| Mobin (2011) UK Ltd | Transport & logistics | 2017 |
| Mocara Limited | Administrative & support | 2007 |
| Mocare Health Ltd | Health & social care | 2023 |
| Mocci Properties Ltd | Real estate | 2025 |
| Mode Construction Solutions Limited | Construction | 2012 |
| Mode Fitness Limited | Arts & recreation | 2026 |
| Modex International Limited | Wholesale & retail | 2017 |
| Modexon Ltd | Wholesale & retail | 2017 |
| Moduhaven Limited | Wholesale & retail | 2023 |
| Modular Therapeutics Limited | Extraterritorial | 2016 |
| Modunite Ltd | Professional & scientific | 2021 |
| Modus Vivendi Installations Limited | Construction | 2007 |
| Mofortrade Ltd | Financial services | 2026 |
| MOG Transports Limited | Transport & logistics | 2024 |
| Mogeco Limited | Wholesale & retail | 2025 |
| Mohamed Riyadh Ltd | Health & social care | 2024 |
| Mole Contractors Limited | | 1980 |
| Mole Electrics Ltd | Construction | 1998 |
| Molinari Business Solutions Ltd | Professional & scientific | 2025 |
| Mollat Limited | Construction | 2022 |
| Molnar's Shipping Ltd | Transport & logistics | 2019 |
| Molt Consultancy Services Limited | Professional & scientific | 2020 |
| Molten Heights Limited | Wholesale & retail | 2016 |
| Momdatech Limited | Information & communication | 2016 |
| Moments.Ai Ltd | Information & communication | 2024 |
| Momentum Business Consulting Ltd | Professional & scientific | 2021 |
| Momentum Procurement Ltd | Professional & scientific | 2017 |
| MON 5 Property Ltd | Households | 2018 |
| Monaco Realestate Limited | Real estate | 2009 |
| MONARCH74 Ltd | Transport & logistics | 2017 |
| Moncrif Close (Bearsted) Management Company Limited | Households | 2007 |
| Moneybrain (L) Ltd | Other services | 2007 |
| Moniker Properties Limited | Real estate | 2019 |
| Monitree App Ltd | Information & communication | 2022 |
| Monks Motors Ltd | Wholesale & retail | 2020 |
| Monnier GAS Engineering Ltd | Construction | 2024 |
| Monobox Limited | Administrative & support | 2025 |
| Monolithic Insulations Ltd | Construction | 2025 |
| Monoprojects Limited | Administrative & support | 2025 |
| Monovision Limited | Financial services | 2026 |
| Monsoon Media Services Limited | Information & communication | 2018 |
| Monsta Graphix Limited | Wholesale & retail | 2025 |
| Montacute Investments Limited | Real estate | 2014 |
| Montara Advisory Limited | Professional & scientific | 2025 |
| Montgo Ltd | Financial services | 2016 |
| Monyz Ltd | Wholesale & retail | 2025 |
| Moochur Ltd | Professional & scientific | 2016 |
| Moochur Merchandise Limited | Professional & scientific | 2024 |
| Mood Group Recruitment Ltd | Administrative & support | 2020 |
| Moon Merry Investments Limited | Wholesale & retail | 2025 |
| Moonfaze Limited | Information & communication | 2022 |
| Moonmix Media Ltd | Professional & scientific | 2026 |
| Moons (London) Limited | Professional & scientific | 2024 |
| Moore Built Limited | Manufacturing | 2026 |
| Moorings Reach Management Company Ltd | Households | 2024 |
| Mopa Ltd | Wholesale & retail | 2020 |
| MOR Property Management Ltd | Real estate | 2021 |
| Mor-Invest Ltd | Financial services | 2012 |
| Moracava Ltd | Transport & logistics | 2026 |
| Morda Ltd | Transport & logistics | 2023 |
| More Eyes Limited | Information & communication | 2018 |
| Moremi Digital Group Ltd | Professional & scientific | 2023 |
| Morgan Alexander Kent Limited | Real estate | 2009 |
| Morgan Hellen Ltd | Information & communication | 2019 |
| Morgan Holdings (SE) Ltd | Financial services | 2023 |
| Morgan Machinery Ltd | Manufacturing | 2000 |
| Morgan Restoration Limited | Construction | 2003 |
| Morgan Thacker Limited | Professional & scientific | 2015 |
| Morgan Williams Partnership Limited | Real estate | 1997 |
| Morondava Homes Ltd | Real estate | 2020 |
| Morondava Limited | Information & communication | 2011 |
| Morondava Property LLP | | 2012 |
| Morris Music Academy CIC | Education | 2026 |
| Morriss Date Management Limited | Financial services | 2026 |
| Morry Management Services Limited | Professional & scientific | 2024 |
| Morsia Fitness Limited | Education | 2020 |
| Morsia Holdings Limited | Financial services | 2019 |
| Morsia Limited | Wholesale & retail | 2019 |
| Mortgage Freeman Ltd | Information & communication | 2019 |
| Mortgage Life UK Limited | Extraterritorial | 2003 |
| Mortimer Brothers Limited | Construction | 2021 |
| Mortley Group Limited | Professional & scientific | 2007 |
| Mortley Holdings Limited | Real estate | 2024 |
| Mortley Plant & Agri Ltd | Administrative & support | 1995 |
| Mortley Plant Hire Limited | Professional & scientific | 2007 |
| Mortley Plant Services Limited | Extraterritorial | 2009 |
| Moss Consulting Engineers Limited | Professional & scientific | 2021 |
| Moss Electrical & Plumbing Ltd | Construction | 2012 |
| Most Desirable Limited | Wholesale & retail | 2013 |
| Mostak Global Group Limited | Hospitality | 2021 |
| Mote Hall Ltd | Professional & scientific | 2001 |
| Mote Park Convenience Store Ltd | Wholesale & retail | 2022 |
| Mote Road Convenience Store Ltd | Wholesale & retail | 2022 |
| Mote Travel Limited | Transport & logistics | 2015 |