| Marcelo Healthcare Limited | Health & social care | 2023 |
| Marcus Telford Estate Agents London Ltd | Real estate | 2017 |
| Marcus Telford Ltd | Real estate | 2022 |
| Margaret Court Property Management Limited | Construction | 2014 |
| Maria Gulina Limited | Wholesale & retail | 2017 |
| Marienas 89 Ltd | Transport & logistics | 2025 |
| Marienas Ltd | Transport & logistics | 2020 |
| Marigold DNM Ltd | Transport & logistics | 2025 |
| Marina International Limited | Wholesale & retail | 2008 |
| Maritime Adjusting Services Holdings Limited | Financial services | 2014 |
| Maritime Adjusting Services Limited | Financial services | 2011 |
| Mark Curtis Roofing Services Limited | Construction | 2025 |
| Mark Thomas Associates Ltd | Professional & scientific | 2020 |
| Market Properties Limited | Real estate | 2016 |
| Marketing United Ltd | Professional & scientific | 2013 |
| Markov Money Limited | Information & communication | 2025 |
| Marr International Ltd | Real estate | 2024 |
| Marvellous Taxi Services Limited | Transport & logistics | 2025 |
| Marwari Rasoi Ltd | Hospitality | 2021 |
| Mary&Jesus Cafe Limited | Hospitality | 2025 |
| Mary's House in the Holy Land Ltd | Professional & scientific | 2022 |
| Masco Management Ltd | Households | 2025 |
| Mash Design Ltd | Professional & scientific | 2006 |
| Masias Technologies Ltd | Manufacturing | 2026 |
| Mast and Tower Safety Limited | Information & communication | 2023 |
| Master Trends Limited | Wholesale & retail | 2025 |
| Matbro Limited | Extraterritorial | 2008 |
| Maureen Glennon Consulting Limited | Information & communication | 2016 |
| MAX Health Resources Ltd | Health & social care | 2013 |
| Maxgo Business Solutions Limited | Information & communication | 2010 |
| Maxinvest Global PLC | Real estate | 2024 |
| Maxoft Technology Ltd | Information & communication | 2020 |
| Maya Solutions Ltd | Information & communication | 2010 |
| Mayakiki Lettings Ltd | Real estate | 2024 |
| Maybe Productions Ltd | Information & communication | 2025 |
| Mayfairn Limited | Professional & scientific | 2018 |
| MAZ Rafi Associates Limited | Other services | 2019 |
| MB Rental Properties Limited | Real estate | 2026 |
| MBD Property Group Ltd | Real estate | 2023 |
| MC IT and Network Solutions Ltd | Construction | 2021 |
| MC4 Heating & Plumbing Ltd | Construction | 2023 |
| MCD Marble Ceramic Design Ltd | Construction | 2021 |
| MCM Safety Consultancy Limited | Public administration | 2026 |
| Mcsm Parcels Ltd | Transport & logistics | 2024 |
| MD Garden Services Limited | Administrative & support | 2020 |
| MD1 Services Ltd | Construction | 2025 |
| MDA Property Limited | Real estate | 2022 |
| Mdoa Ltd | Information & communication | 2023 |
| MDV Heating & Plumbing Ltd | Construction | 2018 |
| Mead Leisure Ltd | Hospitality | 2018 |
| Mech Consulting Limited | Professional & scientific | 2021 |
| Media in & OUT Ltd | Information & communication | 2018 |
| Medina Helal Meat Limited | Wholesale & retail | 2023 |
| Medipro London Ltd | Wholesale & retail | 2023 |
| Mediterranean & Greek Food Ltd | Hospitality | 2024 |
| Mediumlink UK Ltd | Wholesale & retail | 2021 |
| Medtrainai Technologies UK Limited | Health & social care | 2025 |
| Mekanag Ltd. | Extraterritorial | 2003 |
| Mekdachi Paints Ltd | Construction | 2024 |
| Mekic Limited | Construction | 2007 |
| MEL Cochran Limited | Professional & scientific | 2012 |
| Melchi Properties Limited | Real estate | 2018 |
| Melete Limited | Information & communication | 2018 |
| Melhem Services Limited | Wholesale & retail | 2024 |
| Melville Consulting Ltd | Professional & scientific | 2021 |
| Melvyn Bulkes Ltd | Professional & scientific | 2021 |
| Mememe Beauty Limited | Other services | 2018 |
| Memento Design & Build Limited | Construction | 2026 |
| Memory Lane Limited | | 1982 |
| Menantic Limited | Professional & scientific | 2016 |
| Merali Advisory Ltd | Professional & scientific | 2025 |
| Meriton Ltd | Real estate | 2022 |
| Meroux Ltd | Construction | 2026 |
| Mersey Beat Limited | Extraterritorial | 1994 |
| Meryem Fresh Fish & Butchers Ltd | Wholesale & retail | 2025 |
| Meryem Fruit and VEG UK Ltd | Wholesale & retail | 2023 |
| Meryem Tasty Bites Ltd | Hospitality | 2025 |
| Meryt Limited | Manufacturing | 2015 |
| MES Consultancy & Training Services Limited | Professional & scientific | 2011 |
| Messy Cutz Ltd | Other services | 2022 |
| Metaj Builders Ltd | Construction | 2021 |
| Metro Lettings Ltd | Real estate | 2020 |
| MEX Car Sales Limited | Wholesale & retail | 2022 |
| Meyerowitz & Co Ltd | Wholesale & retail | 2000 |
| Mezzopieno Ltd | Wholesale & retail | 2024 |
| Mfgrips Limited | Information & communication | 2018 |
| Mflavius Construct Ltd | Construction | 2023 |
| MG & SS Homes Limited | Real estate | 2024 |
| MH Lighting Ltd | Information & communication | 2011 |
| MH RX Limited | Wholesale & retail | 2018 |
| Michejevas Security Services Ltd | Administrative & support | 2012 |
| Microcement Pro Ltd | Wholesale & retail | 2020 |
| Midland Wire Cordage Company Limited | Extraterritorial | 1986 |
| Mijaba Ltd | Wholesale & retail | 2024 |
| Mika Studio Ltd | Professional & scientific | 2024 |
| Mill Plat Avenue & Linkfield Road Freehold Limited | Real estate | 2026 |
| Millar Associates Property Limited | Real estate | 2020 |
| Million Parts Ltd | Wholesale & retail | 2020 |
| Millionaire Mother Masterclass Limited | Information & communication | 2024 |
| Mimis Lounges Limited | Hospitality | 2023 |