| Mgle Limited | Health & social care | 2024 |
| MGS Electrical Installations Limited | Construction | 2001 |
| MGS Partnership Ltd | Other services | 2023 |
| MH Carpentry & Joinery Ltd | Construction | 2017 |
| MH Design Management Solutions Ltd | Professional & scientific | 2024 |
| MH Houses Ltd | Real estate | 2021 |
| MH1 Management Ltd | Households | 2025 |
| MHG Corporate Risks Limited | Professional & scientific | 2002 |
| MHJ Dedham Limited | Administrative & support | 2021 |
| MHL Holdco Limited | Health & social care | 2013 |
| MI Roofing Limited | Construction | 2025 |
| Miaandlily Ltd | Professional & scientific | 2024 |
| Miand Trans Ltd | Transport & logistics | 2024 |
| MIB Lorry Professional Detailing Ltd | Wholesale & retail | 2019 |
| Mich Care Limited | Health & social care | 2019 |
| Michael Barnard Tax Consulting Limited | Professional & scientific | 2024 |
| Michael Clark Residential Ltd | Real estate | 2020 |
| Michael D Design Services Ltd | Professional & scientific | 2025 |
| Michael Deegan ICT Solutions Ltd | Information & communication | 2026 |
| Michael Eales Architects Ltd | Professional & scientific | 2019 |
| Michael J Fitch Ltd | Arts & recreation | 2025 |
| Michael J Page Computers Limited | Wholesale & retail | 1999 |
| Michael Rgis' Care Ltd | Administrative & support | 2018 |
| Michael Robinson Building Limited | Construction | 2021 |
| Michaels Financial Ltd | Financial services | 2020 |
| Michaels Lettings & Property Management Limited | Real estate | 2014 |
| Michaels Property Consultants Braintree Ltd | Real estate | 2016 |
| Michaels Property Consultants Colchester Limited | Real estate | 2020 |
| Michaels Property Consultants Halstead Ltd | Real estate | 2021 |
| Michaels Property Consultants Limited | Real estate | 2013 |
| Michaels Property Consultants Wivenhoe Ltd | Real estate | 2015 |
| Michaelstowe Lane (Ramsey) Management Company Limited | Households | 2021 |
| Michelin Freelance Ltd | Professional & scientific | 2017 |
| Micra Consultants Ltd | Professional & scientific | 2019 |
| Micra Properties Ltd | Real estate | 2018 |
| Micro Scooters Trustees Limited | Professional & scientific | 2025 |
| Micro Technology Ltd | Professional & scientific | 2003 |
| Microsign Technology Limited | Information & communication | 1997 |
| Microtech Engineering Systems Limited | Manufacturing | 1996 |
| Microtechaligator Limited | Extraterritorial | 2012 |
| MID and North Essex Mind | Health & social care | 1997 |
| MID Essex Building Services Limited | | 1979 |
| MID Tendring Education Partnership | Education | 2012 |
| Midcards Ltd | Wholesale & retail | 2020 |
| Middle East Development Services | Health & social care | 2000 |
| Middle Meadow Management Company Ltd | Real estate | 2022 |
| Middlesex Court RTM Company Limited | Households | 2024 |
| Midessexkitchen Limited | Hospitality | 2017 |
| Midsummer Property Ltd | Real estate | 2012 |
| Midwinter Financial Planning Ltd | Professional & scientific | 2019 |
| Mierenneukers Limited | Information & communication | 2001 |
| Miesam Global Resources Ltd | Administrative & support | 2022 |
| Mighty Electrical Limited | Construction | 2026 |
| Migkind Ltd | Professional & scientific | 2025 |
| Mikail Homes Ltd | Real estate | 2020 |
| Mikail Medica Limited | Health & social care | 2015 |
| Mike Aremu Ltd | Administrative & support | 2021 |
| Mike O'Callaghan Consulting Ltd | Professional & scientific | 2025 |
| Mike Squirrell Limited | Health & social care | 2008 |
| Mikeco Ltd | Professional & scientific | 2019 |
| Mikes Car Room Ltd | Wholesale & retail | 2024 |
| Mikinch Ltd | Administrative & support | 2017 |
| Milbank Concrete Products Limited | Manufacturing | 2001 |
| Milbank Group Limited | Professional & scientific | 2012 |
| Milbank Ventures Limited | Professional & scientific | 2012 |
| Milcomms PR Ltd | Professional & scientific | 2025 |
| Mildmay BOC Ltd | Real estate | 2022 |
| Milestones (Poringland) Management Company Limited | Households | 2018 |
| Milking-It Ltd | Administrative & support | 2020 |
| Mill Court (Braintree) Block 25-30 RTM Company Limited | Households | 2015 |
| Mill Court (Braintree) RTM Company Ltd | Households | 2015 |
| Mill House View (Sudbury) Management Company Ltd | Households | 2024 |
| Mill Reef Management Ltd | Professional & scientific | 2003 |
| Mill Road (Colchester) Management Company Ltd | Households | 2006 |
| Mill Stream (Oxford) Limited | Real estate | 2017 |
| Mill Street Stores Ltd | Wholesale & retail | 2022 |
| Mill View Investments Limited | Construction | 2017 |
| Millennium Court (Clacton) Residents Limited | Households | 2017 |
| Millennium Excelsior Care Limited | Real estate | 1998 |
| Millennium Investments 2000 Ltd | Real estate | 1998 |
| Miller Construction Services Limited | Construction | 1993 |
| Millers Green (Weeley Heath) Management Company Limited | Households | 2018 |
| Millkits 3D Printing Limited | Manufacturing | 2019 |
| Mills & Kirby Builders Limited | Construction | 2007 |
| Mills and Kirby Limited | Construction | 1999 |
| Millshore Limited | Real estate | 2015 |
| Millwheels Ltd | Administrative & support | 2019 |
| Milne Mortgages Ltd | Professional & scientific | 2023 |
| Milsom People Limited | Administrative & support | 2022 |
| Milton Lodge Limited | Health & social care | 2014 |
| Mind & Psyche Care Solutions Ltd | Administrative & support | 2026 |
| Mind Blossom Media Limited | Information & communication | 2024 |
| Mind Connect Health Hub Ltd | Health & social care | 2026 |
| Mind Professionals Limited | Administrative & support | 2004 |
| Mind, Body, Soul & Spirit Limited | Health & social care | 2009 |
| Minden Business Solutions Ltd | Information & communication | 2018 |
| Minder Finance Limited | Financial services | 2026 |
| Mindset Mastery Ltd | Other services | 2025 |
| Mindsett Limited | Administrative & support | 2019 |
| Mineral Services Limited | Real estate | 1992 |