| Mapleton House Freeholders Limited | Real estate | 2009 |
| Mapleton House Management Company Limited | Households | 2004 |
| Marblejar Holdings Limited | Real estate | 2017 |
| Marc Nicholson Lighting Ltd | Information & communication | 2012 |
| Marco Limited | Manufacturing | 1998 |
| Marinos F&C Ltd | Hospitality | 2026 |
| Markshire Limited | Real estate | 1982 |
| Marlpit Hill Building Services Ltd | Construction | 2013 |
| Martell Ventures Limited | Information & communication | 2013 |
| Martell-Surtees Interiors Limited | Professional & scientific | 2026 |
| Martyn Jackson and Associates Limited | Professional & scientific | 2025 |
| Master Confections Limited | Wholesale & retail | 2017 |
| Mathew Harrington Property Ltd | Real estate | 2025 |
| Mayne AV Ltd | Information & communication | 2015 |
| MBH Carry GP, Limited | Real estate | 2019 |
| MBH Co-Invest GP, Limited | Real estate | 2019 |
| MBH Co-Invest LP | | 2019 |
| Mcgourty Projects Ltd. | Transport & logistics | 2013 |
| ME YOU US Ltd | Health & social care | 2024 |
| Medical Aesthetics J.W. Limited | Administrative & support | 2019 |
| Meekins Ltd | Financial services | 2024 |
| Meekins Shah Accountancy Ltd | Professional & scientific | 2011 |
| Melld Limited | Professional & scientific | 2024 |
| MELLD2 Limited | Real estate | 2024 |
| Mercury Consulting Limited | Information & communication | 1995 |
| Merfen Security Ltd | Construction | 2024 |
| Merlin Drive Management Limited | Households | 2022 |
| Merlin Products Limited | Administrative & support | 1994 |
| Metal Consulting Ltd | Professional & scientific | 2024 |
| Metanoia Solutions Ltd | Professional & scientific | 2023 |
| Metrotech Limited | Construction | 2015 |
| Meyritz Consulting Ltd | Professional & scientific | 2013 |
| Microecon Limited | Financial services | 1996 |
| Milakata Ltd | Real estate | 2017 |
| Miles Martial Arts-East Grinstead Ltd | Other services | 2023 |
| Mintbridge Limited | Real estate | 1970 |
| Mirac Berra Limited | Hospitality | 2025 |
| Miss Isabel Aesthetics Ltd | Other services | 2023 |
| Mitodex Limited | Real estate | 2012 |
| MKT Consulting Limited | Construction | 2022 |
| Mlla Limited | Financial services | 2018 |
| MN71 Limited | Construction | 2024 |
| Modify Projects Limited | Construction | 2017 |
| Mojozize Ltd | Information & communication | 2015 |
| Moliner Court Management Limited | Households | 1971 |
| Moment Digital Limited | Information & communication | 2012 |
| Monabel Ltd | Real estate | 2003 |
| Montrose Makers LLP | | 2022 |
| MOO HR Limited | Administrative & support | 2025 |
| Moore Burger Ltd | Hospitality | 2025 |
| Mortehoe Properties Limited | Real estate | 1988 |
| Mountweald Limited | Households | 2009 |
| MR Computing Ltd | Information & communication | 2006 |
| Mskb Consultants Limited | Real estate | 2011 |
| My Plaice OR Yours Ltd | Hospitality | 2025 |
| Myra IT Solutions Ltd | Information & communication | 2019 |
| N.H.A. Associates Limited | Professional & scientific | 1989 |
| Nailtopia Ltd | Other services | 2024 |
| Napier-Clark Ltd | Arts & recreation | 2020 |
| National Cooling Solutions Limited | Energy | 2023 |
| Nationwide Air Conditioning Limited | Construction | 2001 |
| Nationwide Air Conditioning Trustees Limited | Administrative & support | 2022 |
| Nationwide Electrical Limited | Other services | 2008 |
| Nationwide Group (UK) Limited | Administrative & support | 2009 |
| Nationwide Technical Products Limited | Administrative & support | 2008 |
| Naughty Tortoise Limited | Administrative & support | 2004 |
| Nautilus Yacht Charter Limited | Administrative & support | 2015 |
| Nautilus Yachting Limited | Administrative & support | 1992 |
| Nedra Services Ltd | Other services | 2024 |
| Nelson Vets Limited | Professional & scientific | 2012 |
| Nephilim Ltd | Professional & scientific | 2013 |
| Nesteg Ltd | Professional & scientific | 2018 |
| Netvector Consulting Limited | Information & communication | 1997 |
| Neurowise Development Ltd | Professional & scientific | 2007 |
| Neverbeendunn Limited | Wholesale & retail | 2022 |
| Newtye Timber Limited | Administrative & support | 2010 |
| Nexus Trading Limited | Wholesale & retail | 2003 |
| Nightingales (Croydon) Management Company Limited | Households | 1992 |
| Noise Monster Ltd | Information & communication | 2020 |
| Nordhus Properties Limited | Construction | 1999 |
| Northern Shore Investment Ltd | Financial services | 2025 |
| Northumberland Court Management Company Limited | Households | 2002 |
| Notting Hill Carry GP, Limited | Real estate | 2022 |
| Notting Hill Co-Invest GP, Limited | Real estate | 2022 |
| NOW in a Minute Theatre Community Interest Company | Education | 2020 |
| Nyesigns Limited | Professional & scientific | 2011 |
| O Meekins Financial Ltd | Financial services | 2017 |
| Oak Haven Collective CIC | Agriculture & fishing | 2024 |
| Obvious Improvements Limited | Extraterritorial | 2011 |
| Ocean Prominence Limited | Information & communication | 2025 |
| Octave Branding Consultants Limited | Arts & recreation | 2009 |
| Oddball Motor Company London Ltd | Administrative & support | 2023 |
| Odja Holdings Limited | Wholesale & retail | 2017 |
| Ohlson Limited | Administrative & support | 2025 |
| Oliver James Furniture Limited | Manufacturing | 2006 |
| Oliverose Versatility Ltd | Administrative & support | 2025 |
| Ombrea Ltd | Wholesale & retail | 2025 |
| Omega Facilities Management Ltd | Manufacturing | 2013 |
| Omurca Ltd | Construction | 2006 |
| One Stop Build & Landscaping Ltd | Construction | 2026 |