| Motion Medical Limited | Health & social care | 2024 |
| Motion Studios Limited | Information & communication | 2019 |
| Moto Trail Ltd | Extraterritorial | 2022 |
| Motormonkey Ltd | Professional & scientific | 2025 |
| Mount Lodge Farm Limited | Health & social care | 2016 |
| Mountain Force Limited | Construction | 2025 |
| Mountain Goat Consulting Ltd | Professional & scientific | 2012 |
| Mountain Movie Limited | Information & communication | 2023 |
| Mountfield Pallets Ltd | Manufacturing | 2017 |
| Mousehole Bungalow Holidays Ltd | Real estate | 2021 |
| Move N Store Ltd | Transport & logistics | 2020 |
| Move U Waste Ltd | Water & waste | 2024 |
| Movecube Ltd | Extraterritorial | 2011 |
| Moveday Removals Ltd | Transport & logistics | 2021 |
| Movement Workshop Ltd | Arts & recreation | 2020 |
| Movers UK (Heathrow) Ltd | Transport & logistics | 2022 |
| Movin on Limited | Transport & logistics | 2003 |
| Movinghub Limited | Information & communication | 2018 |
| Mozena Ltd | Administrative & support | 2019 |
| MP Engineering Design Limited | Professional & scientific | 2026 |
| MP Heat & GAS Limited | Construction | 2020 |
| MPC Mega Project Construction Ltd | Construction | 2025 |
| MPG Aviation Ltd | Arts & recreation | 2018 |
| MPR IT Solutions Limited | Information & communication | 2008 |
| MPR Professional Services Ltd | Information & communication | 2017 |
| MPR Sports Limited | Wholesale & retail | 2024 |
| MPR Technical Services Limited | Information & communication | 2013 |
| MPU Web Limited | Information & communication | 2013 |
| MR Auto (London) Ltd | Administrative & support | 2015 |
| MR Cash & Carry and Butcher Shop Limited | Wholesale & retail | 2025 |
| MR Consultancy and Sales Ltd | Professional & scientific | 2025 |
| MR Desi Limited | Wholesale & retail | 2014 |
| MR M.M.Ribeiro Steady Transport Services Limited | Transport & logistics | 2025 |
| MR P'S Power Cleaning Limited | Administrative & support | 2025 |
| MR Sparkie Ltd | Extraterritorial | 2021 |
| MR Trans Management Limited | Wholesale & retail | 2023 |
| MRL Acoustics Limited | Professional & scientific | 2009 |
| MRM Estates Ltd | Construction | 2023 |
| MRS & Co Investment Ltd | Real estate | 2025 |
| MRS Consultancy Limited | Real estate | 2023 |
| MRT Group Ltd | Information & communication | 2012 |
| MS Supplier Group Ltd | Wholesale & retail | 2026 |
| MSB Construction Group Ltd | Construction | 2022 |
| Msbm Rentals Ltd | Real estate | 2025 |
| MSC Pro Holdings Ltd | Construction | 2018 |
| Mscos Dental Services Ltd | Health & social care | 2026 |
| Mscos Property Services Limited | Real estate | 2026 |
| MSE Commercial Solutions Limited | Construction | 2019 |
| MSE Maintenance Limited | Construction | 2012 |
| MSK Procurement Limited | Administrative & support | 2013 |
| MSL Media Limited | Administrative & support | 2005 |
| MSR (Kent) Limited | Health & social care | 2022 |
| MT Electrics Ltd | Construction | 2024 |
| MTA Network Ltd | Wholesale & retail | 2018 |
| Mtad Estates Ltd | Real estate | 2020 |
| MTC Taxis Ltd | Transport & logistics | 2020 |
| MTD 2025 Ltd | Professional & scientific | 2022 |
| Mtdee Consulting Ltd | Information & communication | 2022 |
| Mtkp Limited | Public administration | 2022 |
| Mtuk Limited | Administrative & support | 2016 |
| Muchmore Property Investments Ltd | Real estate | 2023 |
| Mucky Pups (Kent) Limited | Other services | 2022 |
| Muddy Boots Welcome Limited | Extraterritorial | 2012 |
| Mudrac Consultancy Limited | Information & communication | 2013 |
| Muhriz Limited | Health & social care | 2024 |
| Muirs Contract Services Ltd | Transport & logistics | 2009 |
| Mulberry Road Management Company Limited | Households | 2026 |
| Muller Office Support Limited | Administrative & support | 2008 |
| Mullery Architects Limited | Professional & scientific | 2018 |
| Multi MAY Limited | Administrative & support | 1997 |
| Multibrand Supplies Ltd | Wholesale & retail | 2026 |
| Multiconsult UK Ltd | Professional & scientific | 2012 |
| Multideck Limited | Construction | 2019 |
| Multimedia Projects Limited | Information & communication | 2005 |
| Multimillionpoundhomes Ltd | Real estate | 2022 |
| Multipac Ltd. | Wholesale & retail | 2015 |
| Multiquoter Limited | Information & communication | 2021 |
| Muncaster Property Management Ltd | Real estate | 2026 |
| Mundy Bois Properties Limited | Real estate | 2015 |
| Mupedza Limited Limited | Health & social care | 2024 |
| Murati Electrical Ltd | Manufacturing | 2016 |
| Murdoch Utilities Ltd | Professional & scientific | 2022 |
| Murrell Holdings Kent Ltd | Financial services | 2017 |
| Murston Business Centre Limited | Households | 2008 |
| Murston Construction Limited | Construction | 1995 |
| Murston Developments (Ingles Manor) Limited | Construction | 2018 |
| Murston Developments (Kent) Limited | Construction | 2016 |
| Muruga Ltd | Financial services | 2024 |
| Musbury Consultants Ltd | Information & communication | 2007 |
| Muscle Coach Limited | Arts & recreation | 2019 |
| Muscle-Tech Fire & Security Ltd | Construction | 2026 |
| Musclehut Ashford Ltd | Arts & recreation | 2023 |
| Muse 7 Publishing Ltd | Information & communication | 2018 |
| Musik Limited | Information & communication | 2023 |
| Muturikwa Limited | Health & social care | 2020 |
| Muziris Gate Limited | Wholesale & retail | 2026 |
| MVC Developments Ltd | Construction | 2021 |
| MVP IT Solutions Limited | Information & communication | 2015 |
| MVP Social Work Consultancy Ltd | Health & social care | 2025 |
| MVW Technology Limited | Information & communication | 2020 |