| Moments Matter Ltd | Wholesale & retail | 2025 |
| Money Tree Consulting Ltd | Financial services | 2014 |
| Montague Jones Limited | Real estate | 2020 |
| Montaigne Press Ltd | Professional & scientific | 1998 |
| Montello Estates Ltd | Construction | 2025 |
| Mooboo Teaz Ltd | Wholesale & retail | 2021 |
| Moody Motorsport Limited | Wholesale & retail | 2025 |
| Mookey Limited | Financial services | 2025 |
| Moonstone SRI Lankan Restaurant Limited | Hospitality | 2007 |
| Moorcroft Equine Rehabilitation Centre | Administrative & support | 1999 |
| Moorcroft Trading Limited | Administrative & support | 2002 |
| Moores Pest Control Services Ltd | Water & waste | 2004 |
| Moorgate Homes Ltd | Real estate | 2014 |
| Moorhouse Industrial Ltd | Real estate | 2016 |
| Moorzen Ltd | Professional & scientific | 2020 |
| Mordor Delivery Partners Ltd | Transport & logistics | 2020 |
| Morgan Peaks Limited | Financial services | 2025 |
| Morganjoslin Ltd | Information & communication | 2018 |
| Morley Farm Eastcourt Ltd | Real estate | 2024 |
| Morleyland Limited | Public administration | 2016 |
| Morningside Decorating Ltd | Construction | 2017 |
| Moroney Holdings Ltd | Real estate | 2023 |
| Morris Capital Group Limited | Financial services | 2024 |
| Morris Palmer Limited | Professional & scientific | 1999 |
| Morrsales Limited | Education | 2023 |
| Mortgage Matters Direct Limited | Extraterritorial | 2000 |
| Mortgage Plus Limited | Financial services | 2012 |
| Mortgage Solutions Holdings Limited | Administrative & support | 2016 |
| Mortgage Solutions Limited | Financial services | 1986 |
| Moses Frank Limited | Professional & scientific | 2010 |
| Moss Auto Services Limited | Wholesale & retail | 2013 |
| Motionoveridleness Ltd | Wholesale & retail | 2024 |
| Motionway Limited | Construction | 2017 |
| Mountain Spring Ltd | Real estate | 2021 |
| Mountfichet Investment Limited | Extraterritorial | 2024 |
| Mowgli Media Ltd | Information & communication | 2024 |
| MPB Digital Ltd | Information & communication | 2022 |
| MPO Recruitment Services Ltd | Administrative & support | 2025 |
| Mpph Ltd | Transport & logistics | 2022 |
| MPR Hove Ltd | Construction | 2025 |
| MR Horsham Ltd | Wholesale & retail | 2026 |
| MR Massage Ltd | Other services | 2024 |
| MR MXF Ltd. | Information & communication | 2016 |
| MRC Accountancy Ltd | Professional & scientific | 2017 |
| MRC Accountancy Services Ltd | Professional & scientific | 2021 |
| MRC Construction Industry Services Ltd | Construction | 2018 |
| Mrmi Consulting Ltd | Information & communication | 2025 |
| Mrwg Construction Limited | Construction | 2025 |
| MS Self Storage Limited | Transport & logistics | 2014 |
| MSL Fire Ltd | Extraterritorial | 2025 |
| Mster Ltd | Wholesale & retail | 2025 |
| MSV Investar Ltd | Arts & recreation | 2003 |
| Msward Consultancy Ltd | Professional & scientific | 2019 |
| Mtpo Civil Engineering Ltd | Construction | 2020 |
| Mtstones Limited | Manufacturing | 2015 |
| Mudpie Fridays Limited | Information & communication | 2017 |
| Mudtree Consulting Ltd | Professional & scientific | 2024 |
| Muggleswick Estate Ltd | Agriculture & fishing | 2005 |
| Mulberry Bush Limited | Wholesale & retail | 1996 |
| Mulberry Close Residents Company Limited | Households | 1961 |
| Mulberry Financial Ltd | Financial services | 2006 |
| Mulcare-Ball Limited | Construction | 2006 |
| Multiple Healthcare Limited | Health & social care | 2014 |
| Multiply Films Ltd | Information & communication | 2025 |
| Mumentum Group Limited | Wholesale & retail | 2026 |
| Mungo's Horsham Ltd | Hospitality | 2026 |
| Munich Legends I.P. Limited | Administrative & support | 2008 |
| Muntham Home Farm Limited | Agriculture & fishing | 2019 |
| Murray Homes Holding Limited | Financial services | 2022 |
| Murray Homes Limited | Construction | 2022 |
| Murray House & Homes Limited | Financial services | 2015 |
| Murray Strategic Management Limited | Professional & scientific | 2024 |
| Music Hub Limited | Information & communication | 2014 |
| Mutiny Consulting Ltd | Information & communication | 2018 |
| Muvin Ltd | Professional & scientific | 2009 |
| Mvii EST. Ltd | Information & communication | 2025 |
| MVZ Properties Ltd | Real estate | 2022 |
| MW Future Limited | Mining & quarrying | 2017 |
| MWB Properties Ltd | Real estate | 2017 |
| My Creatine Co Ltd | Manufacturing | 2026 |
| My Creatine Ltd | Manufacturing | 2025 |
| My Creatine UK Ltd | Manufacturing | 2026 |
| My Employees Wellbeing Ltd | Health & social care | 2025 |
| My First Furniture Ltd | Manufacturing | 2021 |
| My Glamour Shop Ltd | Wholesale & retail | 2025 |
| My Life Story Ltd | Information & communication | 2025 |
| Mycarematters 2020 CIC | Information & communication | 2019 |
| Mycarematters Trading Ltd | Health & social care | 1990 |
| Mycroft Group Ltd | Financial services | 2022 |
| Myelly Limited | Information & communication | 2022 |
| Mygrowthagency Ltd | Professional & scientific | 2026 |
| Mymir Limited | Hospitality | 2024 |
| Myrecruit Team Ltd | Administrative & support | 2026 |
| Mythorabilia Limited | Wholesale & retail | 2023 |
| N DOE Caravans Limited | Wholesale & retail | 2012 |
| N Farley Ltd | Administrative & support | 2002 |
| N Francis Electrical Limited | Professional & scientific | 2012 |
| N J Balfour Ltd | Agriculture & fishing | 2026 |
| N-Mist Limited | Information & communication | 2023 |
| N. Ramsay and J. Spratt Limited | Health & social care | 2022 |