| Lush Skin & Laser Ltd | Other services | 2024 |
| Luxe Quarters Ltd | Hospitality | 2025 |
| Luxury Topping Limited | Extraterritorial | 2016 |
| LV Barbers Limited | Other services | 2015 |
| LV Hair Hampton Limited | Other services | 2025 |
| M&J Capital Ltd | Professional & scientific | 2022 |
| M.M. COX Properties Limited | Construction | 1985 |
| M.M.C. Investments Limited | Professional & scientific | 1973 |
| M@E Projects Ltd | Administrative & support | 2021 |
| Maci Real Estate Ltd | Real estate | 2017 |
| Mackay 143 Ltd | Information & communication | 2023 |
| MAD About Mountains Ltd | Administrative & support | 2015 |
| MADE4NEED Limited | Wholesale & retail | 2023 |
| Madori Homes Ltd | Extraterritorial | 2016 |
| Maebee Limited | Information & communication | 2025 |
| Magashi Ltd | Professional & scientific | 2019 |
| Magis Property Limited | Real estate | 2020 |
| Magnetic Holdings Ltd | Extraterritorial | 2018 |
| Magnisol Limited | Information & communication | 2017 |
| Mahirah Limited | Hospitality | 2018 |
| MAID2CLEAN W London Ltd | Administrative & support | 2013 |
| Mailinner Limited | Households | 1998 |
| Maize Property Management Ltd | Households | 2025 |
| Majority World Community Interest Company | Professional & scientific | 2006 |
| Malabar Construction Limited | Construction | 2001 |
| Malao Investments Ltd | Real estate | 2019 |
| Malik Trading Limited | Wholesale & retail | 2015 |
| Mandamus Limited | Professional & scientific | 2002 |
| Manhab Limited | Real estate | 2024 |
| Manley Talks Limited | Professional & scientific | 1999 |
| Manly Turners Ltd | Real estate | 2017 |
| Manor Lodge Stoughton Residents Association Limited | Households | 1961 |
| Manorah Ltd | Administrative & support | 2025 |
| Mantaq Consulting Ltd | Information & communication | 2019 |
| Mantombazana Ltd | Health & social care | 2026 |
| Maracatu Ltd | Hospitality | 2023 |
| Maren Trading Limited | Administrative & support | 1990 |
| Marie Wills Limited | Professional & scientific | 2017 |
| Maritimesolutionsltd Ltd. | Professional & scientific | 2020 |
| Marjahan Limited | Hospitality | 2025 |
| Market Impact Services Limited | Professional & scientific | 2024 |
| Marketing Means More Limited | Professional & scientific | 2022 |
| Markham Charles Barns Limited | Real estate | 2022 |
| Marlow House (Surbiton) Residents Association Limited | Households | 1962 |
| Marne House Management Limited | Households | 2024 |
| Marprook Property Co. Limited | Real estate | 1958 |
| Marquis Court (Kingston) Limited | Households | 1971 |
| Martins Bookkeeping and Accountancy Limited | Professional & scientific | 2011 |
| Marton Building Services Ltd | Construction | 2015 |
| Mase Moajjels Properties Ltd | Real estate | 2022 |
| Matador BHC Ltd | Real estate | 2018 |
| Materials Testing and Technical Services Ltd | Professional & scientific | 2010 |
| Matip Ltd | Wholesale & retail | 2021 |
| Matt & MIR Construction Limited | Real estate | 2025 |
| Mayar BE of Assistance Ltd | Administrative & support | 2016 |
| Maycomb Limited | Real estate | 2016 |
| MAZ Ltd | Information & communication | 2009 |
| MB Creative Finances Ltd | Real estate | 2019 |
| Mcar London Ltd | Professional & scientific | 2019 |
| Mclaren Architecture Studio Ltd | Professional & scientific | 2024 |
| Mcpa (II) Limited | Real estate | 2014 |
| Mcpa Group Limited | Financial services | 2026 |
| Mcpa Limited | Real estate | 2013 |
| Mcrp Limited Partnership | | 2007 |
| MED About Food Ltd. | Hospitality | 2012 |
| Medaview Property Limited | Real estate | 2026 |
| Media Universal Limited | Professional & scientific | 2026 |
| Media Universal Services Limited | Professional & scientific | 1979 |
| Medireal Limited | Real estate | 2010 |
| Megamusic International Limited | | 1991 |
| MEL Health Limited | Health & social care | 2019 |
| Melon Pharma Ltd | Professional & scientific | 2013 |
| Meminio Limited | Wholesale & retail | 2018 |
| Merchant & Daughters Limited | Hospitality | 2017 |
| Merdeka Investments Ltd | Real estate | 2017 |
| Merit Hill Properties (UK) Ltd | Extraterritorial | 2017 |
| Merlandos Ltd | Wholesale & retail | 2024 |
| Meshtech Ltd | Extraterritorial | 2019 |
| MET Holdings Ltd | Extraterritorial | 2017 |
| Metapraxis Ensemble Ltd | Education | 2019 |
| Metric Flooring Contracts Limited | Construction | 2014 |
| Mexxa Limited | Professional & scientific | 2010 |
| MG Management Services Ltd | Information & communication | 2017 |
| MG REG Consulting Ltd | Professional & scientific | 2024 |
| Michael Hughes Architecture Ltd | Professional & scientific | 2008 |
| Micro XYZ Ltd | Information & communication | 2025 |
| MID Mediation and Counselling Ltd. | Other services | 1999 |
| Mike Bayon Garden Design South Ltd | Administrative & support | 2021 |
| Milbank Carpets Limited | Wholesale & retail | 1995 |
| Millie's Cleaners Ltd | Administrative & support | 2026 |
| Milton Keynes Events Limited | Arts & recreation | 2010 |
| Mindlover Limited | Arts & recreation | 2014 |
| Ming Ying Studio Ltd | Arts & recreation | 2023 |
| Miri UK Construction Limited | Construction | 2019 |
| Mirim Properties Ltd | Real estate | 2017 |
| Miss. Worley Services Limited | Information & communication | 2012 |
| Mission Critical Advisory Limited | Administrative & support | 2026 |
| Mitech Engineering Services Limited | Manufacturing | 2010 |
| MJT Risk Limited | Other services | 2014 |
| MK Nails & Spa Ltd | Other services | 2026 |