| Manor House Westfield Limited | Construction | 2015 |
| Manorsmith Investment Limited | Real estate | 2021 |
| Manorsmith Property Ltd | Real estate | 2024 |
| Marbles Property Management LLP | | 2022 |
| Marchants Builders Limited | Construction | 2002 |
| Margin Building Services Ltd | Construction | 2014 |
| Marina Heights (ST. Leonards) Limited | Households | 1997 |
| Markleigh Developments Limited | Real estate | 2012 |
| Marsh Bookkeeping Services Limited | Professional & scientific | 2003 |
| Marsh Insurance Services (Kent) Limited | Administrative & support | 2007 |
| Marsh Insurance Services Kent (Holdings) Limited | Financial services | 2009 |
| Marshview Construction Limited | Construction | 2010 |
| Martin & SON (Sussex) Limited | Construction | 2003 |
| Martin Hawkins Building Limited | Construction | 2003 |
| Marudean Court Limited | Extraterritorial | 1995 |
| Mary Bowen Limited | Education | 2003 |
| Masonix Ltd | Information & communication | 2006 |
| Matrix Land and Homes Ltd | Construction | 2019 |
| Maximus Property Management LLP | | 2023 |
| Maxwell Court Freehold Limited | Households | 1997 |
| Maxwell Cross Holdings | Real estate | 2018 |
| Mcabs Hastings Ltd | Transport & logistics | 2019 |
| Mcdonald and Hamilton Commercial Estates Limited | Real estate | 2019 |
| Mcdonald and Hamilton Estates Limited | Real estate | 2016 |
| Mckimmie Construction Limited | Construction | 2008 |
| Mcshane Investment Limited | Real estate | 2024 |
| MDO Property Services Ltd | Real estate | 2024 |
| Meap Holdings Limited | Professional & scientific | 2022 |
| Mechanically Minded Limited | Professional & scientific | 2014 |
| Medcap Advisory LLP | | 2021 |
| Medical Consent Limited | Information & communication | 2020 |
| Medical World 4 U Limited | Administrative & support | 2003 |
| Meentaugh Investment Limited | Real estate | 2022 |
| Meentaugh Property Management LLP | | 2022 |
| Meister Holdco Limited | Financial services | 2025 |
| Meister Limited | Wholesale & retail | 2002 |
| Melisande Construction Ltd | Construction | 2019 |
| Melisande Limited | Real estate | 2009 |
| Melisande Property Group Ltd | Construction | 2019 |
| Melray Properties Limited | Real estate | 2022 |
| Melray Property Partnership LLP | | 2022 |
| Meridian JSO Ltd | Real estate | 2023 |
| Metal DE Seda Limited | Wholesale & retail | 2013 |
| Metz Hastings 1066 Properties LLP | | 2018 |
| MF Financial Associates Limited | Financial services | 2019 |
| Michael & Lisa Harrison Properties Limited | Real estate | 2007 |
| Mido Developments Limited | Real estate | 2015 |
| Millers Keep (Pevensey) Management Company Limited | Households | 2011 |
| Millstone Living Ltd | Real estate | 2022 |
| Millstone Property Management LLP | | 2022 |
| MIN Mining Limited | Real estate | 2017 |
| Mindjournal Ltd | Manufacturing | 2016 |
| Mjgs Homes Limited | Real estate | 2022 |
| MK12 Management Ltd | Real estate | 2016 |
| MK12 Property LLP | | 2017 |
| Modern Bespoke Joinery Limited | Construction | 2024 |
| Molforus Ltd | Financial services | 2026 |
| Monopoleigh Estates Limited | Real estate | 2003 |
| Moons Hill Estates Limited | Real estate | 2016 |
| Morrell Properties Limited | Real estate | 2017 |
| Mount Ephraim Projects Limited | Real estate | 2007 |
| Mount Ephraim Property Management LLP | | 2021 |
| Mountview Construction Limited | Construction | 2020 |
| MT Holdings Group Ltd | Financial services | 2026 |
| Mtac Property Holdings Limited | Real estate | 2022 |
| Mtac Property Partnership LLP | | 2022 |
| Mushroom Castle Ltd | Construction | 2020 |
| Mushroom Castle Management Company Limited | Households | 2022 |
| Music Patron | Arts & recreation | 2025 |
| MVP Promotions Limited | Arts & recreation | 2022 |
| N & D Mason Limited | Wholesale & retail | 2006 |
| Nadine's of Minster Limited | Wholesale & retail | 2005 |
| Nailbourne Properties Ltd | Real estate | 2025 |
| Narwan Property Management LLP | | 2021 |
| Nashes Property Company Ltd | Construction | 2018 |
| Nathan Interactive Ltd | Information & communication | 1997 |
| Navex Systems Limited | Information & communication | 2010 |
| NC Group International Limited | Wholesale & retail | 2001 |
| Need a Coach Limited | Education | 2002 |
| Newlands Cardiac Diagnostics Ltd | Health & social care | 2025 |
| Niavalex Investment Limited | Real estate | 2021 |
| Niavalex Limited | Real estate | 2025 |
| Niavalex Property Management LLP | | 2021 |
| Nichols & Bowles Investments Limited | Construction | 2003 |
| Nicol Design Associates Limited | Professional & scientific | 2007 |
| Nigel Clarke Hairdressing Limited | Other services | 2003 |
| Nightswood Limited | Real estate | 2019 |
| Nobbs Family Holdings Ltd | Real estate | 2021 |
| Nobbs Family Partnership LLP | | 2021 |
| Nobis Media Limited | Information & communication | 2018 |
| Noogles Investment Ltd | Real estate | 2019 |
| Norn Distribution Partners UK Limited | Professional & scientific | 2024 |
| Norn Ventures Limited | Administrative & support | 2023 |
| Nova Property International Limited | Real estate | 2017 |
| NR Holding Group Ltd | Financial services | 2026 |
| Nuburu Energy Limited | Administrative & support | 2011 |
| O'Hanlon Property Management LLP | | 2020 |
| Oaten Architects Limited | Professional & scientific | 2014 |
| Ocelot Advisory Limited | Professional & scientific | 2011 |
| Oikos Estates Ltd | Real estate | 2024 |