| Merlin Carpets (Debden) Limited | Wholesale & retail | 2004 |
| Merry Goldberg Ltd | Manufacturing | 2006 |
| Mersea Island Bowling Club,Limited | Arts & recreation | 1932 |
| Metabuy Limited | Wholesale & retail | 2025 |
| Metallic Solutions Ltd | Construction | 2006 |
| Metbrand Products Limited | | 1991 |
| Metis Knowledge Solutions Ltd | Professional & scientific | 2023 |
| Metmar AMZ Limited | Wholesale & retail | 2025 |
| Metpark Limited | | 1981 |
| Metro Properties Limited | Hospitality | 1999 |
| Metropolitan Masonry Limited | Manufacturing | 1965 |
| Metrosparks Ltd | Construction | 2026 |
| Mevar Consulting Ltd | Construction | 2025 |
| Mexx Investments Ltd. | Real estate | 2000 |
| Meze Utilities Ltd | Construction | 2020 |
| Mezzie Ltd | Construction | 2017 |
| Mfsr Consulting Ltd | Professional & scientific | 2018 |
| MG Electrical Solutions Ltd | Construction | 2007 |
| MGK Health Limited | Health & social care | 2018 |
| MGK Sales and Services Ltd | Wholesale & retail | 2025 |
| MH Sarwar Ltd | Wholesale & retail | 2026 |
| MI Telecom Limited | Information & communication | 1991 |
| Miah & Begum FI LLP | | 2017 |
| Miami Ibosha Ltd | Hospitality | 2019 |
| Micanopy Publishing Limited | Information & communication | 2005 |
| Micdan Care Ltd | Health & social care | 2018 |
| Michael Cafferkey (Saffron Walden) Limited | | 1976 |
| Michael Carrick Limited | Arts & recreation | 2008 |
| Michael Ford (Essex) Ltd | Construction | 2003 |
| Michael Lane Limited | | 1973 |
| Michael Wilding Limited | Real estate | 2017 |
| Michele Hair & Beauty Limited | Other services | 2003 |
| Michurs Ltd | Wholesale & retail | 2026 |
| Micolli Ventures Ltd | Real estate | 2026 |
| Micron Cleaning Services Limited | Administrative & support | 2000 |
| Microwave Centre | | 1990 |
| Midas Autos Ltd | Wholesale & retail | 2015 |
| Midpoint Services Limited | Wholesale & retail | 1985 |
| Miedah Limited | Health & social care | 2025 |
| Migration & Contingency Planning Limited | Information & communication | 2007 |
| Mikdash Group Ltd | Real estate | 2026 |
| Mike Carribean Services Limited | Hospitality | 2025 |
| Mike Scully Logistics Limited | Transport & logistics | 2017 |
| Mike's Boatyard Limited | Manufacturing | 1973 |
| Milai Culture Media Co Ltd | Wholesale & retail | 2025 |
| Milano Cento Limited | | 1988 |
| Milecastle Limited | | 1974 |
| Millennium Nail Spa Ltd | Other services | 2018 |
| Millennium Retail Limited | Wholesale & retail | 2005 |
| Miller Electrical Ltd | Administrative & support | 2004 |
| Miller Motor Group Limited | Wholesale & retail | 1998 |
| Miller Property Consultants Limited | Professional & scientific | 1999 |
| Millhead Estates Limited | Construction | 1999 |
| Mills Building & Maintenance Limited | Construction | 1995 |
| Millway Decor Limited | | 1972 |
| Millwood House Residents Company Limited | Households | 2002 |
| Milwod Constructions Ltd | Manufacturing | 2023 |
| Mimo Holdings Limited | Health & social care | 2025 |
| Mind TEC Ltd | Professional & scientific | 2014 |
| Mindjuicer Limited | Information & communication | 2001 |
| Mine & Stake Limited | Information & communication | 2021 |
| Ming Properties Limited | Real estate | 1996 |
| Mingles Events Limited | Other services | 1983 |
| Mini Swimming North Essex LLP | | 2022 |
| Ministers Academy Limited | Professional & scientific | 2025 |
| Minthill Ltd | Hospitality | 2021 |
| Minty Global Limited | Wholesale & retail | 2026 |
| Mintz Consultancy Limited | Administrative & support | 2004 |
| Mira Taylor Limited | Manufacturing | 2006 |
| Mirage Heating & Plumbing Supplies Ltd | Wholesale & retail | 2000 |
| Miraj Trade Limited | Wholesale & retail | 2026 |
| Mirror Door Systems Ltd. | Manufacturing | 1994 |
| Mish Mish Limited | Construction | 2006 |
| Miss AU Decho Limited | Hospitality | 2013 |
| Mistral Maintenance Limited | Construction | 2008 |
| Miswak Club Limited | Wholesale & retail | 2015 |
| Mitchell S a Limited | Wholesale & retail | 2005 |
| Mitek Metro Limited | Professional & scientific | 2006 |
| Mitha Limited | Information & communication | 2004 |
| Mithra Stores Ltd | Wholesale & retail | 2024 |
| Mizacco Limited | Wholesale & retail | 2026 |
| Mizen Trading Limited | Construction | 1999 |
| MJ Holdings (London) Limited | Real estate | 2012 |
| Mjcp Limited | Information & communication | 2009 |
| MJD Painters Limited | Wholesale & retail | 1998 |
| MJG UK Services Limited | Construction | 2017 |
| MJT Engineering and Project Solutions Limited | Manufacturing | 2008 |
| MJU Catering Ltd | Hospitality | 2019 |
| MK Carpets London Limited | Construction | 2024 |
| MKR Designs Limited | Manufacturing | 2004 |
| MKS Fruits & VEG Limited | Wholesale & retail | 2024 |
| Mlamacrafts Ltd | Manufacturing | 2025 |
| Mlow Consulting Limited | Real estate | 2019 |
| MM Apparel & Glow Limited | Wholesale & retail | 2026 |
| MM Logistics World Ltd | Transport & logistics | 2025 |
| MM Meat and Poultry Ltd | Wholesale & retail | 2019 |
| MMS Ockndon Ltd | Hospitality | 2025 |
| MMS Payroll Services Limited | Administrative & support | 1999 |
| Mmusa Limited | Wholesale & retail | 2026 |
| MN Law Ltd | Professional & scientific | 2016 |