| Mannas Kitchen Ltd | Hospitality | 2024 |
| Manningtree Body Repair Centre Ltd | Professional & scientific | 2023 |
| Manor (2016) Holdings Limited | Financial services | 2016 |
| Manor Barns Estate Limited | Other services | 2013 |
| Manor Place Management Company Limited | Households | 1996 |
| Manorcourt Care (Norfolk) Limited | Health & social care | 2002 |
| Manorcourt Homecare Ltd | Extraterritorial | 2015 |
| Manpowerhunt Ltd | Administrative & support | 2018 |
| Mansee Consultancy Ltd | Information & communication | 2011 |
| Mansfield Developments (East Anglia) Limited | Construction | 2006 |
| Mansion Investment Ltd | Real estate | 2023 |
| Mansouri Design Limited | Construction | 2023 |
| Mansun Property Services Ltd. | Real estate | 2019 |
| Mantaray Marine Ltd | Manufacturing | 2018 |
| Mantaray SW Ltd | Administrative & support | 2022 |
| Manuka Games Limited | Information & communication | 2026 |
| Manygrow Ltd | Professional & scientific | 2025 |
| Maomao Holding Ltd | Financial services | 2026 |
| MAP Fabrications Limited | Manufacturing | 2006 |
| MAP Pro Limited | Information & communication | 2019 |
| Mape Luxury Ltd | Hospitality | 2025 |
| Maple Commercial Group Ltd | Construction | 2002 |
| Maple Court (Silvanglen) Residents Association Limited | Households | 1990 |
| Maple Developments (East Anglia) Ltd | Construction | 2004 |
| Maple Healthcare Limited | Health & social care | 2009 |
| Maple Track Services Limited | Construction | 2024 |
| Maplesin Clothings Ltd | Wholesale & retail | 2024 |
| Maponga Ltd. | Health & social care | 2013 |
| Maragota Properties Limited | Agriculture & fishing | 2004 |
| Maram Engineering Limited | Professional & scientific | 2024 |
| Marant Management Limited | Extraterritorial | 2010 |
| Maratha Travels Ltd | Transport & logistics | 2023 |
| Marc Samuel London Limited | Construction | 2020 |
| Marchioness Enterprises Limited | Real estate | 2025 |
| Marcus Watkins Design Ltd | Professional & scientific | 2010 |
| Mardair Limited | Real estate | 1992 |
| Marevauk Ltd | Wholesale & retail | 2025 |
| Marfleet and Bradshaw (1) Limited | Construction | 2023 |
| Marfleet and Bradshaw (2) Limited | Construction | 2023 |
| Marfleet and Bradshaw (Ashford) Limited | Construction | 2023 |
| Marfleet and Bradshaw (Colchester) Limited | Construction | 2023 |
| Marfleet and Bradshaw Limited | Construction | 2007 |
| Marfleet Building Contractors LLP | | 2004 |
| Marfleet Civil Engineering Limited | Construction | 2012 |
| Marfleet Construction Limited | Construction | 2018 |
| Marfleet Contractors Limited | Construction | 2017 |
| Marfleet Developments Limited | Construction | 2017 |
| Margaretting Property Limited | Construction | 2024 |
| Margella Consult Ltd | Administrative & support | 2023 |
| Maria Pharmaceuticals Ltd | Health & social care | 2023 |
| Marie Davies Consulting (UK) Limited | Professional & scientific | 2012 |
| Marie Davies Interim Limited | Administrative & support | 2022 |
| Marina Health Ltd | Health & social care | 2020 |
| Marina One (Chelmsford) Management Company Limited | Households | 2002 |
| Marine Conservation Research International | Administrative & support | 2011 |
| Marine Conservation Research Ltd | Administrative & support | 2009 |
| Marine Court (Frinton) Limited | Households | 1991 |
| Marine Facilitator Ltd | Manufacturing | 2015 |
| Marine Parade Flats (Clacton) Limited | Households | 1980 |
| Marine Propulsion Products Ltd | Manufacturing | 2018 |
| Marine Reef Equine Limited | Wholesale & retail | 2014 |
| Marine Residents (Clacton)Limited | Households | 1970 |
| Mariners Court Residents Association (Aldeburgh) Limited | Extraterritorial | 1981 |
| Mariners Wharf Management Company (Newhaven) Limited | Households | 2002 |
| Marionicholas Trans Ltd | Transport & logistics | 2021 |
| Mark Alistair Holdings Limited | Financial services | 2021 |
| Mark Bowyer Estate Agents Limited | Real estate | 2003 |
| Mark Burton Mortgage and Protection Services Limited | Financial services | 2021 |
| Mark Canham GAS Services Limited | Construction | 2002 |
| Mark Cardy Consultancy Ltd | Professional & scientific | 2016 |
| Mark Dollar Consultancy Limited | Professional & scientific | 2023 |
| Mark Farthing Property Services Limited | Administrative & support | 2016 |
| Mark Klesel & Co Ltd | Professional & scientific | 1999 |
| Mark Lane Commodities Limited | Financial services | 2023 |
| Mark Lees Photography Ltd | Professional & scientific | 2003 |
| Mark Lesley Holdings Limited | Financial services | 2024 |
| Mark Nayler Plumbing & Complete Property Services Limited | Construction | 2005 |
| Mark Nicholas Design Limited | Wholesale & retail | 1999 |
| Mark Watchorn Limited | Professional & scientific | 2012 |
| Mark Whittle & Daughters Roofing Limited | Construction | 2012 |
| Markestra Ltd | Wholesale & retail | 2025 |
| Market Circle Ltd | Wholesale & retail | 2023 |
| Market Data Pro Ltd | Information & communication | 2020 |
| Market Hill Right to Manage Company Ltd | Households | 2021 |
| Marketing Agency PVT Ltd | Wholesale & retail | 2023 |
| Marketleaf Ltd | Education | 2024 |
| Marks Farm Retreat Limited | Hospitality | 2022 |
| Marks Hall Shooting Syndicate Limited | Agriculture & fishing | 2006 |
| Marks TEY Enterprises Ltd | Wholesale & retail | 2010 |
| Marks TEY Gardens Company Limited | Administrative & support | 1967 |
| Marks TEY Healthcare Limited | Wholesale & retail | 2014 |
| Marks TEY Pharmacy Limited | Health & social care | 1998 |
| Marks TEY Products (Fencing & Packing Cases) Ltd | Manufacturing | 2023 |
| Markshall Trading Ltd | Other services | 2011 |
| Marlborough Estates (Ipswich) Limited | Households | 2004 |
| Marlin Investments Ltd | Real estate | 2018 |
| Marlow Neurodevelopment Ltd | Health & social care | 2018 |
| Marney Homes Ltd | Construction | 2025 |
| Maroma Ltd | Construction | 2015 |
| Marquee Carpets Limited | Wholesale & retail | 2011 |