| MJ Signs Limited | Wholesale & retail | 2014 |
| MJC Music Limited | Other services | 2016 |
| MJC Touring Limited | Other services | 2016 |
| MJS Innovations Limited | Financial services | 2024 |
| MK Personnel Solutions Ltd | Administrative & support | 2006 |
| MKA Systems Limited | Information & communication | 2016 |
| MLC Property Limited | Real estate | 2018 |
| MLC Real Estate Ltd | Real estate | 2023 |
| MLG Finance Ltd | Professional & scientific | 2026 |
| MMB Business Consultancy Ltd | Professional & scientific | 2026 |
| MMK Nutri-Health Ltd | Wholesale & retail | 2019 |
| Mmmima Ltd | Information & communication | 2024 |
| MNJV3 Corporation Limited | Hospitality | 2014 |
| Mnrt Music LLP | | 2014 |
| Mobitech I.T. Ltd | Information & communication | 2007 |
| Modern Classics UK Limited | Wholesale & retail | 2009 |
| Modern Eco Design Limited | Professional & scientific | 2024 |
| Modus Verde Ltd | Professional & scientific | 2025 |
| Moegm Limited | Construction | 2018 |
| Moegm UNA Developments Limited | Construction | 2018 |
| Mohan Tamanna LLP | | 2025 |
| MOI MOI Sauce Ltd | Manufacturing | 2019 |
| Mokuzai Ltd | Wholesale & retail | 2020 |
| Molesey Avenue Residents (West Molesey) Limited | Households | 1977 |
| Molesey Boat Club 1866 Limited | Arts & recreation | 2023 |
| Momantai Limited | Professional & scientific | 2024 |
| Moment Marketing Ltd | Professional & scientific | 2025 |
| Momo Shop Limited | Wholesale & retail | 2017 |
| Monarch Butterfly Ltd | Administrative & support | 2021 |
| Monckton Advisory Ltd | Professional & scientific | 2026 |
| Mondo Media Group Limited | Administrative & support | 2026 |
| Moneysums Ltd | Information & communication | 2015 |
| Monster Magic Limited | Arts & recreation | 2025 |
| Monte Generoso Limited | Financial services | 2019 |
| Montgold Capital Holdings Ltd | Real estate | 2016 |
| Montgold Capital LLP | | 2007 |
| Montgomery Hayles Surveyors (Surrey) Ltd | Professional & scientific | 2018 |
| Montgomery Press Ltd | Wholesale & retail | 2021 |
| Montiglobal Ltd | Professional & scientific | 2018 |
| Montpelier Court Homes Limited | Households | 2003 |
| Monument Advisory Group LLP | | 2025 |
| Moon Marketing Management Ltd | Administrative & support | 2016 |
| Moonaura Pictures Ltd | Information & communication | 2021 |
| Moonland Property Ltd | Real estate | 2024 |
| Moor Westfield Ltd | Administrative & support | 2011 |
| Morden Education Limited | Education | 2022 |
| More Revenue Less Cost Limited | Professional & scientific | 2008 |
| Morrowind Services Limited | Financial services | 2023 |
| Mors Software Ltd | Information & communication | 2022 |
| Mortimer Whittaker O'Sullivan Limited | Professional & scientific | 1989 |
| Mosaic Layers Ltd | Information & communication | 2026 |
| Mosaik Consulting Ltd | Professional & scientific | 2021 |
| Mosaiko Consulting Limited | Information & communication | 2023 |
| Moss Bros Finance Limited | Other services | 2020 |
| Motherly Care Ltd | Health & social care | 2025 |
| Motivate Innovate Limited | Professional & scientific | 2024 |
| Mouja Ltd. | Wholesale & retail | 2016 |
| Mould Free Health Ltd | Professional & scientific | 2017 |
| Mount Villas Limited | Real estate | 1985 |
| Mountview Freehold Limited | Households | 2005 |
| Mouva Limited | Information & communication | 2026 |
| Move LDN Holdings Limited | Financial services | 2023 |
| Move LDN Limited | Real estate | 2023 |
| Move Like Water Limited | Health & social care | 2025 |
| Move London Ltd | Real estate | 2009 |
| Movemingle CIC | Health & social care | 2025 |
| Moving Beans Limited | Wholesale & retail | 2017 |
| Movingimageco.Com Limited | Information & communication | 2010 |
| MPH Strategic Advisory Ltd | Professional & scientific | 2022 |
| MPO Business Consulting Ltd | Professional & scientific | 2018 |
| MR Faisal Idrees Ltd | Health & social care | 2019 |
| MR Green Consultancy Ltd | Administrative & support | 2016 |
| MR Sun Ltd | Hospitality | 2026 |
| Mr.Taster Ltd | Wholesale & retail | 2024 |
| MRS Flowers Media Ltd | Information & communication | 2021 |
| MRS. a Beauté Ltd | Wholesale & retail | 2022 |
| Mrs.K Limited | Real estate | 2023 |
| MRV Design Ltd | Wholesale & retail | 2023 |
| MSD Refurbishments Limited | Administrative & support | 2015 |
| Msjp Development Ltd | Construction | 2021 |
| Msjp Pro Ltd | Real estate | 2018 |
| MSM Consultants (UK) Limited | Professional & scientific | 2007 |
| Mszar Investment Ltd | Real estate | 2023 |
| MTC Holdings Limited | Financial services | 2016 |
| Mtcprop (R.I) Limited | Real estate | 2016 |
| Mtcprop (U.I) Limited | Real estate | 2016 |
| Mtouch Ltd | Information & communication | 2026 |
| Muddy Paws Dog Walking Ltd | Other services | 2022 |
| Muffler Trading Limited | Administrative & support | 2021 |
| Muir Woods Limited | Administrative & support | 2019 |
| Mulberry Court HW Management Limited | Administrative & support | 2021 |
| Mulberry Homes (Redhill) Ltd | Construction | 2019 |
| Mulberry Homes (Ruscombe) Limited | Construction | 2025 |
| Mulberry Homes (West Chiltington) Limited | Construction | 2025 |
| Mulberry Recruitment Limited | Administrative & support | 2005 |
| Mulberry Walk Ltd | Real estate | 2024 |
| Multi-Choice Trading Limited | Wholesale & retail | 2023 |
| Multihog Limited | Manufacturing | 2018 |
| Multiply Talent Ltd | Administrative & support | 2024 |
| Muntaner 210 Limited | Real estate | 2016 |