| Maggiebates Ltd | Professional & scientific | 2025 |
| Maghna Ltd | Hospitality | 2023 |
| Magic Blue Ltd | Real estate | 2017 |
| Magic Hair Limited | Wholesale & retail | 2023 |
| Magic Scisors Limited | Other services | 2026 |
| Magic Tavern Ltd | Information & communication | 2020 |
| Maglia Rosso Holidays Ltd | Administrative & support | 2016 |
| Magnatesmedia Ltd | Information & communication | 2022 |
| Magnetic Properties (GL) Limited | Manufacturing | 2020 |
| Magnetic Properties LONDON1 Ltd | Real estate | 2023 |
| Magnetic Tide Limited | Information & communication | 2003 |
| Magnum Cleaners Ltd | Administrative & support | 2025 |
| Magnus News Agency Limited | Other services | 2017 |
| Magnus Rose Limited | Wholesale & retail | 2024 |
| Magpye IO Ltd | Wholesale & retail | 2023 |
| Magrip Ltd | Wholesale & retail | 2025 |
| Maha Homes Ltd | Real estate | 2026 |
| Mahdex Ltd | Information & communication | 2025 |
| MAHFUJURRAHM535 Ltd | Information & communication | 2024 |
| Mahim Ltd | Wholesale & retail | 2025 |
| MAID4PERFECTION Cleaning Limited | Administrative & support | 2025 |
| Maileditor Ltd | Information & communication | 2025 |
| Mailshot Limited | Professional & scientific | 1996 |
| Main SET Swim Ltd | Wholesale & retail | 2026 |
| Maintro Services Ltd | Administrative & support | 2026 |
| Maise Allround Cleaning Services Ltd | Transport & logistics | 2023 |
| Maison Bleue Limited | Manufacturing | 1998 |
| Maison ET Maison Limited | Construction | 2024 |
| Maison FOX Limited | Extraterritorial | 2020 |
| Maison JET Property Ltd | Real estate | 2026 |
| Maison K Limited | Wholesale & retail | 2026 |
| Maisoni Ltd | Wholesale & retail | 2026 |
| Maiven Inclusion CIC | Information & communication | 2025 |
| Maiya UK Ltd | Other services | 2011 |
| Majestic Digital Ltd | Information & communication | 2020 |
| Majestic Edge Ltd | Wholesale & retail | 2025 |
| Majestic Properties Limited | Real estate | 2005 |
| Major Oak Polishing Limited | Construction | 2025 |
| Majors Mews Management Limited | Households | 2019 |
| MAK Trading Solutions Ltd | Wholesale & retail | 2021 |
| Makariou Property Group Ltd | Real estate | 2024 |
| Make ME Train Limited | Education | 2025 |
| Make My Day Limited | Information & communication | 2000 |
| Make My Day Music Ltd | Information & communication | 2015 |
| Make My Day Publishing Limited | Information & communication | 2010 |
| Make Things UN Ltd | Information & communication | 2023 |
| Makepeace BID Services Limited | Administrative & support | 2025 |
| Maker Marketplace Ltd | Professional & scientific | 2024 |
| Maketrix Limited | Wholesale & retail | 2026 |
| Makky Retail Ltd | Wholesale & retail | 2026 |
| Maklad Ltd | Real estate | 2026 |
| Maknt Ltd | Wholesale & retail | 2025 |
| Mako Trades Limited | Information & communication | 2026 |
| Malacapps Ltd | Information & communication | 2026 |
| Malik & SON Group Ltd | Real estate | 2024 |
| Mall Consultants Ltd | Professional & scientific | 2019 |
| Mallcomm Limited | Information & communication | 2000 |
| Mallory Pryce Ltd | Professional & scientific | 2019 |
| Mallow Baby Ltd | Information & communication | 2022 |
| Malti Trading Limited | Wholesale & retail | 2010 |
| Maltings Digital Ltd | Information & communication | 2026 |
| Maluel Limited | Manufacturing | 2026 |
| Malvibe UK Ltd | Wholesale & retail | 2025 |
| Malvybe Limited | Wholesale & retail | 2025 |
| Malyka Ltd | Wholesale & retail | 2025 |
| Mama's Rice Limited | Hospitality | 2021 |
| Mamizu Ltd | Health & social care | 2022 |
| MAN Construction Limited | Construction | 2014 |
| MAN Developments Limited | Construction | 2015 |
| Manamind Limited | Information & communication | 2025 |
| Mane Data Consultancy Ltd | Financial services | 2023 |
| Mane Event Group Ltd | Other services | 2025 |
| Mane Frame Ltd | Information & communication | 2024 |
| Manebae Ltd | Wholesale & retail | 2026 |
| Manfrotto Distribution Limited | Professional & scientific | 1982 |
| Mango Digital Group Ltd | Information & communication | 2026 |
| Manhattan Negae OR Ltd | Information & communication | 2025 |
| Maninex Equip Ltd | Wholesale & retail | 2025 |
| Maniscope Global Ltd | Wholesale & retail | 2025 |
| Maniverge Co Ltd | Wholesale & retail | 2025 |
| Manmade Digital Limited | Professional & scientific | 2023 |
| Manns Property Services Limited | Professional & scientific | 2012 |
| Manor Farm Drive (Beyton) Management Company Limited | Households | 2011 |
| Manor Gardens (Ipswich) Management Company Limited | Real estate | 2002 |
| Manor House Home Fragrance Limited | Wholesale & retail | 2007 |
| Manor House Management Co. Ltd | Administrative & support | 2019 |
| Manor Investment Capital Ltd | Administrative & support | 2021 |
| Mansard Building Solutions Limited | Construction | 2019 |
| Mansfield 4X4 (Bury ST Edmunds) Limited | Wholesale & retail | 2009 |
| Mansur Roastery & Sweets Ltd | Wholesale & retail | 2024 |
| Mantas Quality Decoration Ltd | Construction | 2022 |
| Mantocore Limited | Extraterritorial | 2017 |
| Mantovani Consulting Ltd | Professional & scientific | 2023 |
| Maná Group UK Ltd | Construction | 2017 |
| Maosongtrade Ltd | Wholesale & retail | 2026 |
| MAP Global Limited | Extraterritorial | 2009 |
| Maple Court (IP1) RTM Company Limited | Households | 2025 |
| Maple Green Management Company Limited | Households | 2021 |
| Maple Grove Holdings Ltd | Real estate | 2025 |
| Maple Mystery Games Limited | Wholesale & retail | 2020 |