| Molesey Coach Trimmers Ltd | Wholesale & retail | 2012 |
| Molligo Project Management Ltd | Information & communication | 2011 |
| Moments Like This Photography Ltd | Professional & scientific | 2025 |
| Momentum PR Limited | Professional & scientific | 2015 |
| Momentum Works Solutions Ltd | Information & communication | 2025 |
| MON Ltd | Information & communication | 2014 |
| Monaco Surveyors Limited | Professional & scientific | 2011 |
| Monarch Place Management Company Ltd | Households | 2024 |
| Monckton Bradley Ltd | Professional & scientific | 2019 |
| Monden Property and Investments Limited | Financial services | 2023 |
| Moneytelligence Limited | Information & communication | 2025 |
| Monosapien Limited | Administrative & support | 2009 |
| Monro Communications Limited | Professional & scientific | 2018 |
| Monster Soup Ltd | Information & communication | 2019 |
| Montague Gilmore Holdings Limited | Extraterritorial | 2010 |
| Montague Gilmore Limited | Hospitality | 2010 |
| Montello Apartments LLP | | 2019 |
| Monteray Homes Ltd | Construction | 2015 |
| Montgomery James Property Ltd | Construction | 2023 |
| Montpelier 333 Investments Limited | Real estate | 2025 |
| Monument Build Limited | Construction | 2014 |
| MOO Consult Ltd | Professional & scientific | 2021 |
| Moonlight Gardens Limited | Arts & recreation | 2021 |
| Mooooch Ltd | Information & communication | 2004 |
| More Products Limited | Professional & scientific | 2015 |
| Morgan Seares Associates Ltd | Extraterritorial | 2013 |
| Morgan-Giles (Property) Limited | Professional & scientific | 1997 |
| Morgantwells Ltd | Professional & scientific | 2020 |
| Morris Robertson Associates Ltd | Financial services | 2015 |
| Mosesray Consulting Limited | Information & communication | 2011 |
| Moss Studio Limited | Professional & scientific | 2022 |
| Mostly Drinks Limited | Hospitality | 2014 |
| Mothersill Properties Limited | Construction | 1954 |
| Motion Diagnostics Limited | Health & social care | 2024 |
| Motion Gamer Limited | Wholesale & retail | 2013 |
| Motivational Coach Limited | Education | 2025 |
| Motogirl Ltd | Wholesale & retail | 2015 |
| Motorspan Limited | Professional & scientific | 2000 |
| Moulin Investments Limited | Real estate | 2006 |
| Mount Cook (Kent) Limited | Professional & scientific | 2024 |
| Mountain Marketing Limited | Information & communication | 1996 |
| Mountfield Place Management Company Limited | Extraterritorial | 2001 |
| MP Geomechanics Limited | Professional & scientific | 2016 |
| MP Tennis Limited | Arts & recreation | 2024 |
| MPA Engineering and Construction Services Limited | Professional & scientific | 2009 |
| Mpat.G Ltd | Information & communication | 2008 |
| Mpec Electrical Ltd | Construction | 2018 |
| MPH Business Consulting Limited | Professional & scientific | 2022 |
| Mpower Accounting Services Ltd | Professional & scientific | 2006 |
| MQ Physiotherapy Services Limited | Other services | 2021 |
| MR Ames Tea Limited | Wholesale & retail | 2016 |
| MR Books Bookshop Ltd | Wholesale & retail | 2022 |
| MR Frank Cross Limited | Health & social care | 2013 |
| MR Mcnamara Flowers Ltd | Wholesale & retail | 2019 |
| Mrca Management Ltd | Real estate | 2025 |
| Mrdc Software Limited | Information & communication | 2007 |
| Mrdc Systems Limited | Wholesale & retail | 2014 |
| MRH Engineers Ltd | Professional & scientific | 2025 |
| Mrudula's Hair and Beauty Ltd | Wholesale & retail | 2025 |
| MS Carpentry and Building Ltd | Construction | 2017 |
| MS Plastic Surgery Ltd | Health & social care | 2018 |
| Ms&S Limited | Wholesale & retail | 2015 |
| MSH Cardiology Limited | Health & social care | 2025 |
| MSI (Kent) Ltd | Arts & recreation | 2020 |
| MSK Imaging Sussex Limited | Health & social care | 2024 |
| MSL Medical Ltd | Health & social care | 2020 |
| MSL Precision Limited | Manufacturing | 2017 |
| MSL Quantum Limited | Professional & scientific | 2020 |
| Msporti Wellness Limited | Arts & recreation | 2023 |
| MT Network Services Ltd | Information & communication | 2016 |
| MTK Health Ltd | Professional & scientific | 2026 |
| MTR Services Ltd | Administrative & support | 2025 |
| MTS Freight Solutions Ltd | Administrative & support | 2013 |
| MUD Ltd | Administrative & support | 2007 |
| Mudhra Investments Ltd | Financial services | 2020 |
| Mugo Properties Limited | Real estate | 2018 |
| Mukherjee Medical Limited | Health & social care | 2020 |
| Mulligolf Ltd | Wholesale & retail | 2024 |
| Mums in Business Network Ltd | Other services | 2025 |
| Mums Physiotherapy Ltd | Health & social care | 2021 |
| Munchmin Ltd | Hospitality | 2023 |
| Munro Acoustics Ltd. | Professional & scientific | 2001 |
| Murdoch Planning Consultants Ltd | Professional & scientific | 2024 |
| Murphy Associates (UK) Limited | Professional & scientific | 2009 |
| Murray John Limited | Transport & logistics | 2006 |
| Murray Work Ltd | Professional & scientific | 2023 |
| Muscawell Limited | Real estate | 1989 |
| Musical Instruction Method Ltd | Education | 2016 |
| Mussenden Oncology Ltd | Health & social care | 2026 |
| Mv&Yotova Ltd | Administrative & support | 2024 |
| My Face Place Ltd | Health & social care | 2024 |
| My Home (Brands) LLP | | 2007 |
| My Homecare Ltd | Health & social care | 2015 |
| Mycotech Europe Ltd. | Extraterritorial | 1998 |
| MYN Tonbridge Ltd | Hospitality | 2016 |
| Mywork (UK) Ltd | Administrative & support | 2014 |
| N & R Raymond Building Services Limited | Construction | 2015 |
| N Armstrong Construction and Refurbishment Ltd | Construction | 2023 |
| N&N IT Limited | Information & communication | 1998 |
| N&S Gents Barbers Ltd | Other services | 2021 |