| Mitchell’S Catering Service’S Limited | Hospitality | 2025 |
| Mitro Utility Management Limited | Energy | 2014 |
| MIU Limited | Other services | 2021 |
| Mixed Essex Limited | Professional & scientific | 2024 |
| MJ Bees Limited | Agriculture & fishing | 2021 |
| MJ Health and Wellbeing Ltd | Health & social care | 2022 |
| Mjbt Incorporated Ltd | Agriculture & fishing | 2019 |
| MJF Pharma Ltd | Professional & scientific | 2025 |
| Mjhc Ltd | Professional & scientific | 2022 |
| MJK Agencies Limited | Wholesale & retail | 2021 |
| Mjkh Management Ltd | Construction | 2025 |
| MJM Bridge Property Solutions Limited | Real estate | 2025 |
| MJM Records Ltd | Information & communication | 2024 |
| MJM UK Holdings Limited | Financial services | 2022 |
| Mjmediahouse Ltd | Other services | 2011 |
| MJT Finance Limited | Financial services | 2019 |
| MJW Consulting (UK) Limited | Transport & logistics | 2002 |
| MJW Investments Limited | Extraterritorial | 2009 |
| MK Brickwork & SON Limited | Construction | 2018 |
| MK Housing Services Ltd | Real estate | 2024 |
| MK MED Services Ltd | Health & social care | 2019 |
| MK Private Finance Ltd | Financial services | 2019 |
| Mkad Tech Solutions Ltd | Information & communication | 2023 |
| MKAYS11 Limited | Health & social care | 2019 |
| Mke's Interior and Home Decor Limited | Manufacturing | 2015 |
| Mkev Limited | Extraterritorial | 2024 |
| MKG Facades Limited | Construction | 2021 |
| MKJ Inventory Ltd | Other services | 2025 |
| Mkline Ltd | Wholesale & retail | 2018 |
| MKM Group Limited | Education | 2022 |
| MKM Recruitment Limited | Administrative & support | 2025 |
| Mkrt Company Ltd | Health & social care | 2016 |
| Mkuk Home Ltd | Real estate | 2019 |
| ML Brickwork (Southern) Ltd | Construction | 2011 |
| ML Brickwork Facades Limited | Construction | 2023 |
| ML Service Solutions Ltd | Wholesale & retail | 2017 |
| MLG Landscapes Limited | Administrative & support | 2021 |
| MM 24 Ltd | Transport & logistics | 2026 |
| MM Blackpool & Preston Ltd | Administrative & support | 2026 |
| MM Global Supermarket Chelmsford Ltd | Wholesale & retail | 2025 |
| MMC South East Limited | Construction | 2018 |
| MMM Rentals Limited | Hospitality | 2024 |
| MN BD IT Solutions Ltd | Information & communication | 2014 |
| MNG Maintenance Limited | Construction | 2016 |
| MNR Technologies Ltd | Information & communication | 2015 |
| MNT UK Consulting Ltd | Professional & scientific | 2015 |
| MO Construction Ltd | Construction | 2015 |
| Moaj Limited | Professional & scientific | 2014 |
| Moat Farm Business Centre Limited | Real estate | 2008 |
| Mobile Automotive Services Ltd | Wholesale & retail | 2014 |
| Mobile Thrones Limited | Administrative & support | 2010 |
| Mobile Tyre Fitting Chelmsford Ltd | Wholesale & retail | 2025 |
| Mobility Made Modern Ltd | Wholesale & retail | 2025 |
| Mobilitypartners Ltd | Professional & scientific | 2024 |
| Mobius (Beaulieu) Limited | Professional & scientific | 2025 |
| Mobrook Global Limited | Financial services | 2019 |
| Moco Shop Limited | Wholesale & retail | 2025 |
| Modach Property Ltd | Real estate | 2026 |
| Modern & Co Holdings Ltd | Financial services | 2026 |
| Modern Storage Ltd | Transport & logistics | 2024 |
| Modernmax Limited | Professional & scientific | 2000 |
| Modex Solutions Ltd | Real estate | 2017 |
| Modifex Trading Limited | Wholesale & retail | 2025 |
| MOE Outdoor Limited | Health & social care | 2024 |
| Moerel Law Limited | Professional & scientific | 2022 |
| Mohanrosy Limited | Real estate | 2019 |
| Mohs Heating and Ventilating Ltd | Construction | 2026 |
| Moleaware Limited | Health & social care | 2005 |
| Molecular Design Limited | Professional & scientific | 2011 |
| Molle PAC Limited | Wholesale & retail | 2023 |
| Molloy's Rigging Ltd | Information & communication | 2018 |
| Momentum Design Management Limited | Professional & scientific | 2003 |
| Momentum Digital Ltd | Professional & scientific | 2025 |
| Momentum Property Investments Ltd | Real estate | 2025 |
| Momentum Tribe Ltd | Wholesale & retail | 2025 |
| Momjack Ltd | Administrative & support | 2022 |
| Mon-Virtual Assistants Ltd | Administrative & support | 2022 |
| Monarch Joss Ltd | Other services | 2019 |
| Monergize Ltd | Professional & scientific | 2019 |
| Money Market Systems Limited | Information & communication | 2014 |
| Monken Hadley Management Company Limited | Households | 2002 |
| Monkey Motorsport Limited | Manufacturing | 2016 |
| Monkey Puzzle Consulting Limited | Professional & scientific | 2021 |
| Mono 08 Limited | Hospitality | 2025 |
| Monoki Limited | Information & communication | 2014 |
| Montagu's Food Company Ltd | Wholesale & retail | 2025 |
| Montarc Limited | Professional & scientific | 2014 |
| Montgomery Financial Consultants Ltd | Financial services | 2019 |
| Montrose T C Ltd | Manufacturing | 1991 |
| Monty Construction Ltd | Construction | 2021 |
| Monty Marketing Limited | Financial services | 2019 |
| Moobba Limited | Wholesale & retail | 2021 |
| Moon Brands Ltd | Wholesale & retail | 2021 |
| Moonbrook Property Ltd | Real estate | 2025 |
| Moonlight Acquisitions (R) Limited | Information & communication | 2023 |
| Moonlight Mile Limited | Arts & recreation | 2017 |
| Moonway Ltd | Wholesale & retail | 2025 |
| Moonwing Limited | Real estate | 2013 |
| Moor Park Developments Ltd | Construction | 2016 |
| Moore Bros Holdings Limited | Financial services | 2020 |