| MGP Logistics Ltd | Professional & scientific | 2021 |
| MGS Services (E.A) Limited | Professional & scientific | 2013 |
| MH Vehicle Diagnostics and Tuning Ltd | Wholesale & retail | 2021 |
| Mhasm Limited | Real estate | 2026 |
| Michael P Watson and Company Limited | Professional & scientific | 2025 |
| Michael Souter Rope Access Limited | Professional & scientific | 2018 |
| Micro Engineering (Great Yarmouth) Limited | Professional & scientific | 2002 |
| Microworks Limited | Information & communication | 2007 |
| Midas Components Limited | Wholesale & retail | 2000 |
| Midas Displays Ltd | Manufacturing | 2012 |
| Midexco Limited | Mining & quarrying | 1974 |
| Midland Orthodontics Limited | Real estate | 2010 |
| Midway Media Ltd | Professional & scientific | 2025 |
| Milano DON Construction Ltd | Construction | 2025 |
| Milano Great Kebab Ltd | Hospitality | 2025 |
| Mill House Pool Hire Limited | Arts & recreation | 2019 |
| Mill House Property Rental Limited | Real estate | 2022 |
| Mill Lane Management Company (Bradwell) Limited | Households | 2008 |
| Miller Civil Engineering & Earthworks (Anglia) Limited | Construction | 2025 |
| Millies Little Dreams Ltd | Wholesale & retail | 2022 |
| Minaba Collection Ltd | Wholesale & retail | 2021 |
| Mini Corner Shop Ltd | Wholesale & retail | 2024 |
| Mini Cuts Ltd | Other services | 2023 |
| Mini Monsters Ltd | Arts & recreation | 2021 |
| Minimart (Norfolk) Limited | Wholesale & retail | 2014 |
| Miranim Limited | Hospitality | 2024 |
| Mirapure Cleaning Services Ltd | Administrative & support | 2026 |
| Mirracoat Limited | Wholesale & retail | 2023 |
| Mississippi River Boats (Horning) Limited | Transport & logistics | 1994 |
| Mixsmiths Ltd | Extraterritorial | 2023 |
| Mizra Limited | Hospitality | 2026 |
| MJ Hotels Limited | Hospitality | 2023 |
| MJD Engineering (Suffolk) Limited | Professional & scientific | 2013 |
| MJM Offshore Solutions Ltd | Professional & scientific | 2026 |
| Mjmultimedia Limited | Information & communication | 2008 |
| MJS Commercial Consultant Ltd | Professional & scientific | 2024 |
| MJS Portfolios Ltd | Real estate | 2016 |
| MJS Propertys Limited | Real estate | 2022 |
| MJS Unity Ltd | Financial services | 2026 |
| MK Holistic Orthodontics Limited | Health & social care | 2022 |
| MK Oilfield Consultants Limited | Construction | 2016 |
| Mkfashionwheel Ltd | Wholesale & retail | 2025 |
| Mkhprojects.Com Limited | Professional & scientific | 2010 |
| Mkkm Limited | Real estate | 2024 |
| MKS Lettings Ltd | Real estate | 2022 |
| Mlfn Consultancy Limited | Extraterritorial | 2019 |
| MLS Electrical Services Ltd | Construction | 2015 |
| MM & MT Sky's Limited | Real estate | 2016 |
| MM ANP Ltd | Administrative & support | 2014 |
| MNO Investments Ltd | Real estate | 2021 |
| Mo:Re Property Developments Ltd | Construction | 2025 |
| MOA Foods Limited | Manufacturing | 2019 |
| Mobile Care Ltd | Wholesale & retail | 2018 |
| Mobile Mobility Solutions Ltd | Wholesale & retail | 2026 |
| Mobile Solutions (EA) Limited | Other services | 2010 |
| Mobilesolutions (GY) Limited | Other services | 2022 |
| Modern Design & Developments Ltd | Construction | 2023 |
| Modulus Technology Limited | Manufacturing | 2016 |
| Molar Power Limited | Health & social care | 2021 |
| Monheim Real Estate Limited | Construction | 2018 |
| Montana Decorator Ltd | Construction | 2026 |
| Monument Futures Ltd | Administrative & support | 2019 |
| Mood Leap Project Ltd | Administrative & support | 2025 |
| Moody Deals Ltd | Arts & recreation | 2019 |
| Moose Developments (Norfolk) Limited | Construction | 2017 |
| Morgan Cooper Limited | Manufacturing | 1987 |
| Morgelli Oilfield Services Ltd | Professional & scientific | 2013 |
| Morleyuk Ltd | Construction | 2025 |
| Mortgage Response Ltd | Financial services | 2017 |
| Mortgage Seeker Limited | Financial services | 1999 |
| Mortgage Specialist Limited | Financial services | 2024 |
| Morton Peto Estate Management Limited | Administrative & support | 2010 |
| Mosbay Ltd | Manufacturing | 2023 |
| Moughton Engineering Limited | Manufacturing | 2006 |
| Mould-Off Ltd | Water & waste | 2025 |
| Moyo Mzuri Limited | Wholesale & retail | 2026 |
| MP Accounting Services Limited | Professional & scientific | 2017 |
| MP Boiler Tech Ltd | Construction | 2024 |
| MPD Builders Limited | Construction | 2019 |
| MR. Wheelie Clean (Broadland DC) Limited | Administrative & support | 2005 |
| MRH Industrial Cleaning Ltd | Administrative & support | 2018 |
| MRH Window Cleaning Ltd | Administrative & support | 2013 |
| MTC Property Limited | Real estate | 2018 |
| MTS Electrical (East Anglia) Limited | Construction | 2013 |
| Multiforce Contracts Holdings Limited | Professional & scientific | 2009 |
| Multiforce Contracts Limited | Manufacturing | 1998 |
| Munch&Mingle Ltd | Hospitality | 2026 |
| Mundey & Co Ltd | Real estate | 2019 |
| Munnings Construction Limited | Construction | 2016 |
| Munnings Developments Limited | Construction | 2019 |
| Munnings Plant Hire Limited | Administrative & support | 2021 |
| Munnings Supplies Limited | Wholesale & retail | 2011 |
| Murrant Family Funeral Services Limited | Other services | 2024 |
| Murray-Smith Consulting Limited | Hospitality | 2015 |
| Murrell Cork & Bros. Limited | Other services | 1968 |
| Murrell Cork Funerals Limited | Extraterritorial | 2019 |
| Murrell Holdings Limited | Financial services | 2015 |
| Musica Britannica Ltd | Arts & recreation | 2018 |
| Musketeer Scents Ltd | Manufacturing | 2024 |
| Muskitari Ltd | Hospitality | 2024 |