| MKG Property Development Ltd | Real estate | 2025 |
| Mksk Ltd | Administrative & support | 2017 |
| MKY Management Ltd | Real estate | 2020 |
| MLY Properties Ltd | Real estate | 2018 |
| MMJ Consulting Ltd. | Professional & scientific | 1996 |
| MMJ1 Limited | Wholesale & retail | 2025 |
| MNK Build Ltd | Construction | 2026 |
| MO 98 Limited | Other services | 2022 |
| Mobisa Ltd | Health & social care | 2022 |
| Modco Trading Limited | Administrative & support | 2006 |
| Modoptics Ltd | Wholesale & retail | 2017 |
| Moffco Limited | Wholesale & retail | 2019 |
| Mohair the Barbers Limited | Other services | 2016 |
| Mojo Digital Ltd | Information & communication | 2025 |
| Mojo Stayz Ltd | Real estate | 2024 |
| Mollart Universal Joints Ltd | Professional & scientific | 2006 |
| Monee 2 Card Limited | Information & communication | 2025 |
| Monet Aesthetics Ltd | Health & social care | 2023 |
| Monnington Investments Limited | Financial services | 2022 |
| Monster Junk Hatfield Ltd | Water & waste | 2023 |
| Montclair Estates Limited | Wholesale & retail | 2025 |
| Montellors Ltd | Education | 2025 |
| Moody's Sports Turf Ltd | Arts & recreation | 2023 |
| Moon Electrical & Renewable Engineering Limited | Manufacturing | 2023 |
| Moonlitsky Limited | Professional & scientific | 2025 |
| Moorhampton Investments Limited | Financial services | 2022 |
| Mopheth Foods Limited | Hospitality | 2024 |
| MOR Industries Ltd | Administrative & support | 2025 |
| More Responsive Staffing Limited | Health & social care | 2023 |
| Morea Limited | Extraterritorial | 2005 |
| Moritz Media Group Limited | Information & communication | 2016 |
| Morningstar Build Ltd | Construction | 2025 |
| Morris Island Consulting Limited | Professional & scientific | 2013 |
| Morter Hargrave Limited | Administrative & support | 2001 |
| Mosaic Spa and Health Club (Shrewsbury) Limited | Arts & recreation | 2011 |
| Motam Woodworks Limited | Manufacturing | 2016 |
| Mother Nature's Drinks Limited | Wholesale & retail | 2017 |
| Motion Tech Limited | Construction | 2026 |
| Motorparks Automobiles Ltd | Wholesale & retail | 1957 |
| Motorquote Limited | Wholesale & retail | 2016 |
| Mount Sion City of Living GOD Church (Msclgc) Limited | Information & communication | 2023 |
| Moveform Limited | Wholesale & retail | 2012 |
| Mozaib Limited | Real estate | 2021 |
| MPD Evolution Limited | Wholesale & retail | 2017 |
| MPN Developments Ltd | Real estate | 2022 |
| Mpro Homes Ltd | Construction | 2017 |
| MR Bygg Ltd | Manufacturing | 2020 |
| MR Food Catering Limited | Wholesale & retail | 2020 |
| MR Jewelery Limited | Wholesale & retail | 2025 |
| MRN Consultancy(Herts) Ltd | Real estate | 2022 |
| Mspe Ltd | Wholesale & retail | 2025 |
| MST Estates Limited | Real estate | 2025 |
| MTA Wholesale Ltd | Wholesale & retail | 2025 |
| Mtech Tuning Ltd | Wholesale & retail | 2024 |
| MTG Blinds and Shutters Ltd | Wholesale & retail | 2022 |
| MTP Automotive Ltd | Wholesale & retail | 2025 |
| Muddi Associates Limited | Information & communication | 2015 |
| Mukry Tech Limited | Wholesale & retail | 2026 |
| MUL Logistics Ltd | Transport & logistics | 2019 |
| Multijobs VAS Ltd | Construction | 2026 |
| Multiplex Properties Limited | Real estate | 1999 |
| Multisparks Electrical Ltd | Construction | 2026 |
| Mundaka Ltd | Information & communication | 2018 |
| Murbit Consultants Limited | Information & communication | 2018 |
| Murlidhar Enterprise Ltd | Wholesale & retail | 2024 |
| Murray Investments Public Houses Ltd | Professional & scientific | 2018 |
| Musaeus College Past Pupils Association UK | Other services | 2024 |
| Muse Sphere Limited | Arts & recreation | 2025 |
| Mustbejohn Ltd | Information & communication | 2022 |
| Muzo Decoration Ltd | Other services | 2020 |
| MVI Broadcast Systems Limited | Information & communication | 2004 |
| MVS Global Limited | Wholesale & retail | 2017 |
| My Dutch Uncle Limited | Administrative & support | 2015 |
| My Pizza Hatfield Ltd | Wholesale & retail | 2024 |
| My Soul Photography Ltd | Professional & scientific | 2025 |
| My Tennis Coaching Ltd | Education | 2022 |
| Myers Real Estates Ltd | Real estate | 2024 |
| Mylan Holdings Acquisition 2 Limited | Financial services | 2016 |
| Mylan Holdings Acquisition Limited | Financial services | 2016 |
| Mylan Holdings Ltd. | Financial services | 2015 |
| Myleads Consulting Ltd | Professional & scientific | 2024 |
| Mzrk Limited | Wholesale & retail | 2023 |
| N & S Brar Ltd | Construction | 2023 |
| N C D Contractors Ltd | Construction | 2015 |
| N&Ck LLP | | 2024 |
| N&J Property Maintenance Ltd | Construction | 2024 |
| N&M Estates Ltd | Real estate | 2017 |
| N&Y Construction Ltd | Construction | 2018 |
| N.G.C. Project Management Limited | Professional & scientific | 2000 |
| N.M.Shah UK Ltd | Professional & scientific | 2018 |
| Naavdi Solutions Limited | Information & communication | 2017 |
| Nacc Merchandise Limited | Wholesale & retail | 1996 |
| NAS Corporate Services Ltd | Administrative & support | 2011 |
| Nasa Marine Limited | Manufacturing | 1990 |
| Nash Bros Limited | Wholesale & retail | 1951 |
| Nasza Dely Hatfield Ltd | Wholesale & retail | 2021 |
| Natly Ltd | Real estate | 2024 |
| Natmagg Solutions Limited | Construction | 2019 |
| Natrix Ecological Limited | Professional & scientific | 2024 |
| Natural Solutions Wellness Events Ltd | Other services | 2026 |