| Moore Electrical Services Ltd | Construction | 2017 |
| Moore Glazing Solutions Ltd | Administrative & support | 2016 |
| Moores Catering Engineers Ltd | Other services | 2024 |
| Moos Beauty Limited | Extraterritorial | 2025 |
| Mootoo Partnership Limited | Financial services | 2021 |
| Moqq Servicing Ltd | Other services | 2024 |
| Moran Rose Ltd | Professional & scientific | 2022 |
| More Laundries Limited | Administrative & support | 2021 |
| More Prosper Limited | Information & communication | 2015 |
| Morena Enterprises Limited | Wholesale & retail | 2003 |
| Moreton Property Limited | Real estate | 2020 |
| Moretti Fine Art Limited | Wholesale & retail | 2004 |
| Morgan Berry Interiors Limited | Construction | 2004 |
| Morgan Clark Foundation | Administrative & support | 2010 |
| Morgan Clark Limited | Administrative & support | 1999 |
| Morgan Crest Unlimited | Real estate | 2011 |
| Morgan Holdings Group Limited | Financial services | 2026 |
| Morgan's Cleaning & Property Services Limited | Administrative & support | 2003 |
| Morganclark Building Services Ltd | Other services | 2011 |
| Morillon UK Limited | Manufacturing | 1987 |
| Morning Racing Limited | Information & communication | 2002 |
| Morrant Group Limited | Wholesale & retail | 1973 |
| Morris Projects Limited | Information & communication | 2009 |
| Morse Digital Security Ltd | Wholesale & retail | 2019 |
| Mortgage Business Financial Advisers Ltd | Financial services | 2015 |
| Mortgage Business Properties Limited | Financial services | 2019 |
| Mortgage Business Residential Limited | Real estate | 2021 |
| Mortgage Thoughts Limited | Professional & scientific | 2015 |
| Mortgages 2.0 Ltd | Financial services | 2024 |
| Mortgease Ltd | Financial services | 2024 |
| Mortimer Place (Hatfield Peverel) Residents Management Company Limited | Households | 2021 |
| Mortlist Ltd | Information & communication | 2023 |
| Morton Lakes Limited | Real estate | 2022 |
| MOS Shop Chelmsford Ltd | Wholesale & retail | 2026 |
| Mosari Ltd | Information & communication | 2016 |
| Mosedale Energy (Holdings) Limited | Financial services | 2022 |
| Mosedale Energy Limited | Construction | 2021 |
| Mosuro Ltd | Information & communication | 2025 |
| Motexa Services Ltd | Professional & scientific | 2025 |
| Mother's Bites Limited | Manufacturing | 2017 |
| Motion Dojo Ltd | Information & communication | 2022 |
| MOTIV8 Fitness Community Ltd | Arts & recreation | 2026 |
| Motoparking Limited | Wholesale & retail | 2013 |
| Motor AID Limited | Wholesale & retail | 2008 |
| Motor Valley Cars Limited | Wholesale & retail | 2023 |
| Motorcycle Web Services Limited | Information & communication | 1999 |
| Motorpay Limited | Other services | 2026 |
| Motortech Services Limited | Wholesale & retail | 2015 |
| Mottram Group Limited | Manufacturing | 2024 |
| Mottram Installation Group (UK) Ltd | Construction | 2023 |
| Moulsham Barn Management Company Limited | Households | 2001 |
| Moulsham Hall Estates Limited | Construction | 2013 |
| Moulsham Hall Farms Limited | Agriculture & fishing | 2001 |
| Moulsham Homes Limited | Real estate | 2024 |
| Moulsham Infant School | Education | 2011 |
| Moulsham Lodge MOT Centre Limited | Wholesale & retail | 2025 |
| Moulsham Mini Mart Limited | Wholesale & retail | 2025 |
| Moulsham Minimarket Limited | Wholesale & retail | 2024 |
| Moulsham Motor Company Limited | Wholesale & retail | 2024 |
| Moulsham News Limited | Wholesale & retail | 2011 |
| Moulsham Plumbing and Heating Ltd | Extraterritorial | 2019 |
| Mount Care and Support Ltd | Health & social care | 2026 |
| Mount Hill Care Limited | Health & social care | 2020 |
| Mount Hill Cleaning Services Limited | Administrative & support | 2026 |
| Mountain ASH Property Company Limited | Real estate | 2021 |
| Mouton IS a Claret Ltd | Wholesale & retail | 2022 |
| Move GP Ltd | Transport & logistics | 2007 |
| Move Masters Essex Ltd | Transport & logistics | 2025 |
| Moveit Removals Limited | Transport & logistics | 2011 |
| Movesample Limited | Construction | 1988 |
| Mowden Hall Limited | Construction | 2024 |
| Moya International Ltd | Wholesale & retail | 2022 |
| Moye Development Projects Ltd | Construction | 2025 |
| MP Waste Management Limited | Water & waste | 2023 |
| MPA Property Limited | Real estate | 2017 |
| MPC Plumbing Limited | Construction | 2005 |
| MPE Developments Limited | Real estate | 2015 |
| MPE Property Ltd | Construction | 2016 |
| MPH Media & Tech Ltd | Information & communication | 2026 |
| MPM Commercial Contracts Ltd | Other services | 2020 |
| MPM Property Group Limited | Construction | 2011 |
| Mpossible Limited | Professional & scientific | 2024 |
| Mpower Interim Limited | Professional & scientific | 2018 |
| Mptech Limited | Professional & scientific | 2010 |
| MR and MRS Cleaning Ltd | Other services | 2016 |
| MR Barnaby's Ltd | Wholesale & retail | 2024 |
| MR Cloth Ltd | Wholesale & retail | 2020 |
| MR Lofts & Installations Ltd | Construction | 2025 |
| MR Ramz Ltd | Hospitality | 2026 |
| MR Ramzz Ltd | Hospitality | 2024 |
| Mrbproductions Limited | Information & communication | 2024 |
| Mreps Trustees (NO 4) Limited | Professional & scientific | 2002 |
| MRF1NUT Models Ltd | Wholesale & retail | 2019 |
| MRI Legal Ltd | Professional & scientific | 2017 |
| Mrradams Ltd | Construction | 2021 |
| MRS Brightside Cleaning Ltd | Administrative & support | 2026 |
| MRS Cook Limited | Professional & scientific | 2025 |
| Mrs.D.V.A.Harrison Limited | Real estate | 1958 |
| MRT World Ltd | Wholesale & retail | 2017 |
| Mrvn Limited | Information & communication | 2017 |