| Mgref 2 Cooks Holdings Limited | Financial services | 2022 |
| Mgref 2 Cooks Investments Limited | Financial services | 2022 |
| MGT Teesside Limited | Energy | 2008 |
| MIB Electrical Engineers Limited | Construction | 1996 |
| Michaela Tornaritis Ltd | Professional & scientific | 2023 |
| Microtec Industries Limited | Professional & scientific | 2011 |
| Microvast Power Systems UK Limited | Manufacturing | 2014 |
| MIK Health Limited | Health & social care | 2022 |
| Mila Violet Limited | Professional & scientific | 2017 |
| Milbel Properties Ltd | Real estate | 2025 |
| Milkwood Road SE24 Limited | Construction | 2022 |
| Millie AMP Electrical Ltd | Construction | 2025 |
| Milton Industrial Properties Ltd | Real estate | 2022 |
| Mind Holdings Ltd | Real estate | 2026 |
| Mind Mechanical Services Group Limited | Construction | 2021 |
| Mindful Pilates Limited | Arts & recreation | 2010 |
| Mindshare Global Limited | Information & communication | 2021 |
| Mineisdifferent Limited | Wholesale & retail | 2025 |
| Ming Foods Limited | Manufacturing | 2004 |
| Mirza Instruments Ltd | Wholesale & retail | 2024 |
| Miss Prim Limited | Wholesale & retail | 2022 |
| Miss Tickets Limited | Wholesale & retail | 2020 |
| Mitm Search Ltd | Information & communication | 2023 |
| MJ & RS Property Ltd | Real estate | 2018 |
| Mj&G Ltd | Real estate | 2023 |
| MK Studio London Ltd | Professional & scientific | 2025 |
| Mkhcs Ltd | Health & social care | 2019 |
| Mmmc Ltd | Hospitality | 2024 |
| Mobile Scaffolding Ltd | Construction | 2026 |
| MOD Education Services Ltd | Education | 2025 |
| Moda Property Developments Limited | Financial services | 2024 |
| Modern Schools (Barnsley) Holdings Limited | Construction | 2004 |
| Modern Schools (Barnsley) Limited | Construction | 2004 |
| Modern Schools (Exeter) Holdings Limited | Construction | 2004 |
| Modern Schools (Exeter) Limited | Construction | 2004 |
| Module Homes Ltd | Construction | 2019 |
| Moni Associates Limited | Information & communication | 2024 |
| Montagu Building Limited | Construction | 2015 |
| Montila Developments Southern Ltd | Construction | 2024 |
| Monumental Bathrooms and Plumbing Services Ltd | Construction | 2021 |
| Moore Accounts Ltd | Professional & scientific | 2018 |
| Moriarty Search Limited | Administrative & support | 2022 |
| Morq Limited | Construction | 2022 |
| Motion Learning Limited | Professional & scientific | 2005 |
| Motiv Search Limited | Administrative & support | 2018 |
| Moushill Investments Limited | Construction | 2012 |
| Mozart Pictures Ltd | Manufacturing | 2025 |
| MPH Plumbing & Heating Limited | Construction | 2016 |
| MR Construction South East Limited | Construction | 2026 |
| MR1PEC Ltd | Arts & recreation | 2025 |
| MRB Construction Services South East Limited | Construction | 2026 |
| MSC Universal Ltd | Health & social care | 2007 |
| Msoriano Ltd | Extraterritorial | 2020 |
| MT Property Developers Limited | Construction | 2020 |
| MT Roofing Limited | Construction | 2006 |
| MTF Diamond Drilling and Controlled Demolition Limited | Construction | 2000 |
| Muay Thai Records Limited | Information & communication | 2025 |
| Mulraj Supermarket (East Horsley) Ltd | Wholesale & retail | 2007 |
| Mutlu Housing Ltd | Construction | 2024 |
| Muttly Ltd | Financial services | 2018 |
| MVT Wonder Kids Ltd | Health & social care | 2025 |
| Mvyt Ltd | Water & waste | 2020 |
| MW & J Services Ltd | Administrative & support | 2015 |
| MWP Roofing Ltd | Construction | 2021 |
| My Abode UK Properties Limited | Real estate | 2020 |
| My Instant Stylist Ltd | Wholesale & retail | 2021 |
| My Place Away (Holdings) Limited | Construction | 2015 |
| My.Surveyor.Ai Ltd | Professional & scientific | 2026 |
| Mypiece Limited | Information & communication | 2015 |
| Mypremises Limited | Real estate | 2023 |
| N&H London Construction Ltd | Construction | 2025 |
| N&T Consultancy Solutions Limited | Professional & scientific | 2016 |
| N.J Joy Limited | Health & social care | 2013 |
| N5 Management Services Ltd | Professional & scientific | 2023 |
| NAI IVA Energy Limited | Wholesale & retail | 2025 |
| Natclean Ltd | Health & social care | 2014 |
| National Skill Mapping Ltd | Professional & scientific | 2023 |
| Nationwide Rooms Limited | Real estate | 2015 |
| Nbmushekhan Limited | Real estate | 2025 |
| NDC Competition Ltd | Wholesale & retail | 2025 |
| NED Futures Consultancy Limited | Financial services | 2001 |
| Neguit Limited | Professional & scientific | 2021 |
| Nelly Investment Services Limited | Information & communication | 2003 |
| Nesting Homes Limited | Real estate | 2025 |
| New Century Cleaning Services Limited | Administrative & support | 2026 |
| New Edgware Road Sushi Ltd | Hospitality | 2024 |
| New Green Interim Holdco Limited | Financial services | 2016 |
| New Leaf Renovations Limited | Construction | 2020 |
| New Oxford Street Sushi Ltd | Manufacturing | 2019 |
| New Rainbow Inn Limited | Hospitality | 2014 |
| Newbay Consulting Limited | Professional & scientific | 2016 |
| Newberry Rantell Ltd | Health & social care | 2024 |
| Newhospitals (ST Helens and Knowsley) Finance PLC | Financial services | 2005 |
| Newhospitals (ST Helens and Knowsley) Holdings Limited | Professional & scientific | 2005 |
| Newhospitals (ST Helens and Knowsley) Limited | Health & social care | 2005 |
| Newhospitals (ST Helens and Knowsley) Nominee Limited | Professional & scientific | 2005 |
| Newimports Limited | Wholesale & retail | 2026 |
| Newschools (Leyton) Holdings Limited | Professional & scientific | 1999 |
| Newschools (Leyton) Limited | Administrative & support | 1999 |
| Newschools (Merton) Holdings Limited | Professional & scientific | 2002 |