| Morris & Young Mechanical Limited | Energy | 2016 |
| Mosford Enterprises Ltd. | Professional & scientific | 2018 |
| Mosscrest Limited | Real estate | 1982 |
| Mosspotality Ltd | Hospitality | 2025 |
| Mother Fit Limited | Administrative & support | 2021 |
| Mother Fit PT Ltd | Arts & recreation | 2024 |
| Motion Electronics Limited | Wholesale & retail | 2025 |
| Motor Industry Management Limited | Professional & scientific | 1984 |
| Motorhouse Limited | Wholesale & retail | 2000 |
| Mount and Co Estate Agents Ltd | Real estate | 2025 |
| Mount and Partner Estate Agents Limited | Real estate | 2022 |
| Mount ROW (Mayfair) Limited | Real estate | 2015 |
| Movecritic Limited | Public administration | 2024 |
| Movewellgb Ltd | Wholesale & retail | 2024 |
| MRH Finance Limited | Financial services | 2023 |
| MSL Property Solutions Ltd | Real estate | 2026 |
| Msmk Limited | Administrative & support | 2018 |
| MSS Property Services Limited | Real estate | 2011 |
| MT Consultancy Services Limited | Professional & scientific | 2025 |
| Mtec Freight Group Limited | Extraterritorial | 2000 |
| Mtec Transport Limited | Extraterritorial | 2000 |
| Mtec Warehousing Limited | Administrative & support | 2000 |
| MTV Cars Limited | Wholesale & retail | 2015 |
| Muhammad Solutions Ltd | Professional & scientific | 2026 |
| Mulberry Tree Developments Limited | Real estate | 2018 |
| Multibag Investments Limited | Financial services | 2017 |
| Murphy and Sons Ltd | Construction | 2009 |
| Murphy and Sons Property Management Limited | Real estate | 2018 |
| Music Concierge Limited | Information & communication | 2007 |
| Music Concierge Worldwide Limited | Financial services | 2013 |
| Music FIX Ltd | Arts & recreation | 2010 |
| Mutate Consulting Ltd | Professional & scientific | 2021 |
| Mutenka Limited | Extraterritorial | 2020 |
| Mutualtake Property Management Limited | Households | 1997 |
| MVF Construction Ltd | Construction | 2021 |
| MWA Financial Advice Ltd | Financial services | 2004 |
| MWA Financial Ltd | Administrative & support | 2020 |
| MWF Innovations Limited | Wholesale & retail | 2014 |
| MWT Legal Ltd | Professional & scientific | 2006 |
| Mxson.Co Ltd | Wholesale & retail | 2025 |
| My Boat Booker Limited | Administrative & support | 2025 |
| My Dream Investment Ltd | Wholesale & retail | 2023 |
| My Later Life Limited | Financial services | 2024 |
| My Later Life Planning Limited | Financial services | 2024 |
| My Site Engineering Ltd | Professional & scientific | 2021 |
| Myco Biotec Ltd | Professional & scientific | 2024 |
| N C Contract Furniture Components Limited | Manufacturing | 2000 |
| N C I Resources Limited | Administrative & support | 1997 |
| N J R Motor Sports Ltd | Wholesale & retail | 1996 |
| N W G Engineering Limited | Professional & scientific | 2018 |
| N&Dh Investments Limited | Administrative & support | 2015 |
| N&M Paradise Ltd | Water & waste | 2012 |
| N. Reynolds Ltd | Construction | 2014 |
| N.E.J. Consultants Limited | Administrative & support | 2018 |
| N.J. Francis (Holdings) Limited | Real estate | 1992 |
| N.L.S.S.M. Limited | Other services | 2017 |
| N.R. Hardy & Co. Ltd | Administrative & support | 2015 |
| N2 Display Graphics Limited | Manufacturing | 2017 |
| N2 Employees' Trustee Limited | Administrative & support | 2025 |
| N2 Group Holdings Limited | Financial services | 2025 |
| N2 Group Limited | Other services | 2015 |
| N2 Visual Communications Limited | Manufacturing | 1996 |
| Nafgold Property Investments Limited | Other services | 2019 |
| Nails Station Ltd | Other services | 2024 |
| Naked Group Limited | Real estate | 2021 |
| Naked Media Communications Ltd | Manufacturing | 2020 |
| Naklo Contracting Ltd | Transport & logistics | 2016 |
| NAM Professional Services Limited | Professional & scientific | 2021 |
| Napoleon Records Limited | Information & communication | 2022 |
| Narya Hart Limited | Real estate | 2022 |
| NAS GAS Solutions Ltd | Construction | 2025 |
| Nascot Wood Mews Management Limited | Households | 1987 |
| Nash-Gardner Limited | Professional & scientific | 2021 |
| Nashdom Design Limited | Administrative & support | 2005 |
| Nashe Livingcare Solutions Limited | Health & social care | 2023 |
| National Fast Bowling Academy Limited | Arts & recreation | 2018 |
| National Game Fair Limited | Arts & recreation | 2015 |
| National Letting Solutions Limited | Real estate | 2024 |
| Nationwide Emergency Education Limited | Education | 2013 |
| Nationwide Personal Searches Limited | Administrative & support | 2006 |
| Naturally Wood Floors Limited | Construction | 1999 |
| Naturally Wood Limited | Construction | 2021 |
| Naylis Ltd | Financial services | 2025 |
| Nbur Consulting Ltd | Professional & scientific | 2022 |
| NCI Technologies Limited | Information & communication | 2004 |
| ND Consultancy Ltd | Professional & scientific | 2020 |
| NDP Accountancy Services Ltd | Professional & scientific | 2024 |
| Neckinger Mills Freehold Limited | Real estate | 2024 |
| Nelp Limited | Professional & scientific | 2018 |
| Neon Healthcare International Ltd | Professional & scientific | 2025 |
| Neon Healthcare Ltd | Manufacturing | 2009 |
| Neon Pharmaceuticals Ltd | Professional & scientific | 2025 |
| Neonsky Capital Ltd | Financial services | 2010 |
| Netville Management & Consultancy Limited | Administrative & support | 2023 |
| Network Deployments Limited | Information & communication | 2009 |
| New Enterprise House RTM Company Limited | Households | 2024 |
| New Image Installation Ltd | Construction | 2023 |
| New Kart Limited | Arts & recreation | 2009 |
| New Nordic Advisors Limited | Administrative & support | 2018 |
| New River Holdings Limited | Financial services | 1950 |