| Modern Upholstery Ltd | Other services | 2026 |
| Modern Warrior Ltd | Wholesale & retail | 2019 |
| Modoy Services Limited | Wholesale & retail | 2011 |
| Modus Consult Ltd | Professional & scientific | 2016 |
| MOK Logistic and Construct Ltd | Construction | 2020 |
| Molly's Car & Commercial Recycling Ltd | Water & waste | 2015 |
| Moment Photography Limited | Professional & scientific | 2019 |
| Momentum Mums Ltd | Wholesale & retail | 2025 |
| Monaghan Developments (Kent) Ltd | Real estate | 2017 |
| Monigva Ltd | Transport & logistics | 2022 |
| Monopoly Amazon Ltd | Extraterritorial | 2025 |
| Monopoly Garages Ltd | Real estate | 2025 |
| Monopoly Just EAT Ltd | Hospitality | 2026 |
| Monopoly Land Limited | Agriculture & fishing | 2026 |
| Monopoly Property Investments Limited | Real estate | 2004 |
| Monopoly Residential Limited | Real estate | 2026 |
| Monster Bait & Tackle Supplies Ltd | Wholesale & retail | 2013 |
| Monterey Lifting Solutions Ltd | Administrative & support | 2015 |
| Mooli Good Ltd | Wholesale & retail | 2020 |
| Moon & Stars Consulting Limited | Professional & scientific | 2017 |
| Moonchild Beauty Limited | Wholesale & retail | 2021 |
| Moot Brew Co Ltd | Manufacturing | 2021 |
| More Secure Cyber Ltd | Information & communication | 2026 |
| More-Tech Engineer Surveyors Ltd | Professional & scientific | 2016 |
| Morello Grill House Ltd | Hospitality | 2022 |
| Morgan & Mason Ltd | Manufacturing | 2018 |
| Morgan and Morgan Mallorca Limited | Real estate | 2013 |
| Morgan Chex Commercial Finance Limited | Financial services | 2015 |
| Morgan Hunt Construction Ltd | Construction | 2019 |
| Morris & SON Developments Ltd | Construction | 2015 |
| Mosaic Community Network Ltd | Education | 2022 |
| Mote Security Limited | Construction | 2025 |
| Moth to Butterfly Ltd | Wholesale & retail | 2016 |
| Motherland Media Group Limited | Hospitality | 2025 |
| Moto-X Rivara Kent Limited | Wholesale & retail | 1995 |
| Motol Care Limited | Public administration | 2019 |
| Mount Construction Management Limited | Professional & scientific | 2011 |
| Move on South East Ltd | Real estate | 2025 |
| Moxy Property Consultants Ltd | Other services | 2019 |
| Moyo Adewuyi Ltd | Health & social care | 2024 |
| MP Jardim Estates Ltd | Real estate | 2023 |
| Mpave Construction Ltd | Construction | 2020 |
| MPC Distribution UK Ltd | Manufacturing | 2025 |
| Mpire Heating Ltd | Construction | 2011 |
| Mpwra-Rtm Company Ltd | Households | 2021 |
| MPX Sups Ltd | Wholesale & retail | 2026 |
| MR Resin Bound & Paving UK Ltd | Construction | 2025 |
| MR Vending & Solution Ltd | Wholesale & retail | 2026 |
| MR World of Jerk Ltd | Hospitality | 2025 |
| Mrel Properties Limited | Real estate | 2024 |
| Mroy Limited | Education | 2018 |
| MRS Property Services Limited | Real estate | 2004 |
| MRZ a Ltd | Transport & logistics | 2022 |
| MS London Services Ltd | Other services | 2026 |
| MS Shokar Ltd | Real estate | 2024 |
| MSK Professionals Limited | Health & social care | 2014 |
| MST Building Services South East Limited | Construction | 2018 |
| Msts 78 Limited | Wholesale & retail | 2020 |
| Mtbo Limited | Transport & logistics | 2020 |
| MTS Cleansing Group Limited | Financial services | 2021 |
| MTS Cleansing Services Limited | Water & waste | 1986 |
| MU25CH Ltd | Other services | 2017 |
| Muhammad Zeeshan Ltd | Wholesale & retail | 2025 |
| Mukhtar Enterprise Limited | Manufacturing | 1989 |
| Mulberry Automotives Ltd | Wholesale & retail | 2010 |
| Multifold Ltd | Health & social care | 2023 |
| Multikonsult Ltd | Wholesale & retail | 2019 |
| Multimixconcrete Ltd | Construction | 2026 |
| Munje UK Limited Limited | Health & social care | 2017 |
| Muntaj Ltd | Construction | 2020 |
| Murphy Ecology Limited | Professional & scientific | 2026 |
| Murphy’S Letting Limited | Real estate | 2025 |
| Muse Creative Communications Ltd | Professional & scientific | 2018 |
| Musicworx Ltd | Information & communication | 2020 |
| Musigroup Ltd | Information & communication | 2026 |
| Musta Ltd | Professional & scientific | 2018 |
| Mustbdark Ltd | Wholesale & retail | 2023 |
| MW Access Services Ltd | Construction | 2024 |
| MW London Ltd | Hospitality | 2022 |
| Mwatts Electrical and Property Solutions Ltd | Construction | 2022 |
| Mwaw Properties Limited | Real estate | 2022 |
| MX Solutions Ltd | Wholesale & retail | 2010 |
| MXL Consultancy Ltd | Administrative & support | 2024 |
| My Turning Point Internship, Study and Employability Company Limited | Education | 2016 |
| Myatt Holdings Ltd | Real estate | 2017 |
| Myrathes Limited | Hospitality | 2020 |
| Myro Homes Ltd | Real estate | 2026 |
| Myrtle Learning Exams Ltd | Education | 2025 |
| Myrtle Learning Limited | Administrative & support | 2012 |
| Myrtle Learning School Limited | Education | 2025 |
| Myrtle Learning Sixth Form Limited | Education | 2025 |
| Myrtle Reading Club Ltd | Education | 2025 |
| Myrtle Recruitment Ltd | Administrative & support | 2024 |
| Mysa Safety Limited | Professional & scientific | 2025 |
| Mytipievent Ltd | Administrative & support | 2015 |
| N J Vass Limited | Health & social care | 2015 |
| N&J Property Solutions Ltd | Real estate | 2021 |
| N(Cubed) Ltd | Information & communication | 2026 |
| N.Eastwood Limited | Transport & logistics | 1964 |
| N.K.S (South East) Limited | Manufacturing | 2012 |