| Mcje Ltd | Professional & scientific | 2020 |
| MCK My Day Ltd | Wholesale & retail | 2025 |
| MCK Property Holdings Limited | Real estate | 2018 |
| Mcnally Joinery Ltd | Construction | 2019 |
| Mconstruct Intl Ltd | Real estate | 2022 |
| MCQ Houses Limited | Real estate | 2026 |
| Mcqueen Hair & Beauty (Orpington) Ltd | Other services | 2018 |
| MCS Holdings(Uk) Limited | Wholesale & retail | 2022 |
| MD Nails Ltd | Other services | 2024 |
| MD Vicius Ltd | Construction | 2024 |
| MDS Renewables Ltd | Construction | 2024 |
| Mdwg Limited | Education | 2015 |
| Meadow Court Residents' Association Limited | Households | 1991 |
| Meadow Garden Services Limited | Administrative & support | 2023 |
| Meadowland Estates Limited | Real estate | 2003 |
| Meckay (Lowfield) Ltd | Professional & scientific | 2025 |
| Meckay Limited | Professional & scientific | 2007 |
| Meckay Properties Ltd | Real estate | 2022 |
| Meclec Collective Ltd | Professional & scientific | 2025 |
| Medan Solutions Limited | Real estate | 2016 |
| Medi Touch Ltd | Professional & scientific | 2024 |
| Media 96 Ltd | Professional & scientific | 2020 |
| Media by Belle Limited | Extraterritorial | 2019 |
| Media Networks Ltd | Information & communication | 2004 |
| Medical and Healthcare Flooring Limited | Construction | 2020 |
| Medical Choices Limited | Health & social care | 2022 |
| Medically Legal Limited | Professional & scientific | 2019 |
| Medics International Limited | Wholesale & retail | 2024 |
| Medisec London Ltd | Administrative & support | 2021 |
| Medistock Online Ltd | Wholesale & retail | 2021 |
| Medistock Solutions Limited | Professional & scientific | 2009 |
| Medixa Ltd | Health & social care | 2021 |
| Meera Fuel Ltd | Wholesale & retail | 2019 |
| Meera Properties Mgmt Ltd | Households | 2020 |
| Mehmood Investments Ltd | Professional & scientific | 2022 |
| Melange Coaching Ltd | Professional & scientific | 2020 |
| Melange Coffee-Bar Ltd | Hospitality | 2018 |
| Melbourne Air Conditioning Ltd | Construction | 2020 |
| Melbury Lettings Limited | Real estate | 2025 |
| Melbury Property Holdings Limited | Financial services | 2025 |
| Melbury Pubs Limited | Real estate | 2020 |
| Melissa Mcgrath Ltd | Real estate | 2018 |
| Melody Duhaney Ltd | Arts & recreation | 2019 |
| Menporul Solutions Ltd | Information & communication | 2010 |
| Mental Healthcare Professionals Limited | Administrative & support | 2019 |
| Mentoractive CIC | Education | 2026 |
| Meopham George PUB Limited | Hospitality | 2024 |
| Merano Ltd | Other services | 2018 |
| Merchant Freight Limited | Transport & logistics | 2018 |
| Mercian Marble & Granite Limited | Manufacturing | 2010 |
| Mercon Air Limited | Construction | 2002 |
| Mercy Corporate Relocation Ltd | Hospitality | 2024 |
| Mercyrose Limited | Public administration | 2024 |
| Merenti Consulting Ltd | Professional & scientific | 2017 |
| Meridian Investments (UK) Limited | Real estate | 2009 |
| Meridian MMI Direct Ltd | Wholesale & retail | 2025 |
| Meridian Rail Services CZ Limited | Manufacturing | 2020 |
| Meridien Logistics Ltd | Administrative & support | 2025 |
| Meritfinance Limited | Financial services | 2025 |
| Merrynz Ltd | Health & social care | 2019 |
| Merston Engineering Limited | Professional & scientific | 2015 |
| Meryworth Services Limited | Administrative & support | 2011 |
| Meshi Homes Ltd | Construction | 2022 |
| Metanoia London Limited | Professional & scientific | 2015 |
| Metapoint Properties Limited | Real estate | 2024 |
| Metapoint Technologies Ltd | Information & communication | 2017 |
| Metro Flooring Limited | Construction | 2007 |
| Metropolitan Networks (UK) Limited | Information & communication | 2003 |
| Metropolitan Property Developments Limited | Construction | 2019 |
| Metropolitan Solar Energy Limited | Extraterritorial | 2010 |
| Meylee International Limited | Wholesale & retail | 2026 |
| MFD Management Limited | Other services | 2014 |
| Mfords Consulting Limited | Professional & scientific | 2013 |
| MG Cars Enthusiasts Club Limited | Information & communication | 1995 |
| MGB Creative Design Ltd | Professional & scientific | 2025 |
| MGM Building Contracting UK Limited | Construction | 2020 |
| MGM Heating Ltd | Construction | 2010 |
| MGM Plant and Tool Hire Limited | Construction | 2010 |
| MH Property Design Limited | Construction | 2024 |
| MH Renovation Ltd | Construction | 2014 |
| MHL Services Holdings Ltd | Financial services | 2025 |
| MHZ Commercials Ltd | Wholesale & retail | 2025 |
| Miah's (Reading) Limited | Hospitality | 2001 |
| Micah James Limited | Financial services | 2011 |
| Mich-Joseph Enterprises Ltd | Real estate | 2016 |
| Mickey VEG Limited | Hospitality | 2003 |
| Microaccounts Ltd | Professional & scientific | 2025 |
| Microcement in London Ltd | Construction | 2018 |
| Micropub Consultancy Limited | Professional & scientific | 2023 |
| MID Kent Homes (1972) Ltd | Construction | 2019 |
| Mida Properties Limited | Real estate | 1972 |
| Midas Beauty & Aesthetics Ltd | Other services | 2025 |
| Midas Systems (London) Limited | Information & communication | 2003 |
| Midesmusic Ltd | Manufacturing | 2020 |
| Midge Auto Limited | Administrative & support | 2015 |
| Midsummer Houses Limited | Real estate | 2020 |
| Migaleq Ltd | Information & communication | 2013 |
| Mighty Sports Group Limited | Wholesale & retail | 2021 |
| Migz World Ltd | Wholesale & retail | 2024 |
| Mikail 2022 Ltd | Hospitality | 2022 |