| Marfa Signature Ltd | Wholesale & retail | 2025 |
| Marga Web Ltd. | Information & communication | 2013 |
| Maria Takaendisa Consultancy Ltd | Health & social care | 2019 |
| Maribella Cosmetics Limited | Wholesale & retail | 2025 |
| Marilink Digital Ltd | Wholesale & retail | 2026 |
| Marine & Industrial Pump Services Ltd | Manufacturing | 2011 |
| Marine Cabling Services Ltd | Professional & scientific | 2011 |
| Marion International Limited | Professional & scientific | 2018 |
| Maritime Health Limited | Health & social care | 2024 |
| Maritime Property Kent Limited | Real estate | 2024 |
| Mark and Steve Properties Ltd | Real estate | 2021 |
| Mark Kinneavy Ltd | Transport & logistics | 2024 |
| Mark Piesley Ltd | Construction | 2006 |
| Mark Ruffell Property Services Ltd | Real estate | 2026 |
| Mark Tuff Limited | Construction | 2007 |
| Marketing AS Sales Support Ltd | Information & communication | 2024 |
| Marketing Masters Consulting Limited | Other services | 2019 |
| Markwood Construction Ltd | Construction | 2023 |
| Marlew Building & Maintenance Limited | Construction | 2003 |
| Marlow Consultancy Limited | Information & communication | 2015 |
| Marlowe Wood Limited | Professional & scientific | 2002 |
| Marlyn Haulage Ltd | Transport & logistics | 2018 |
| Marma Logistic Ltd | Transport & logistics | 2024 |
| Marmalad Ltd | Transport & logistics | 2019 |
| Marmox (UK) Ltd | Wholesale & retail | 2000 |
| Maroke Ltd | Wholesale & retail | 2022 |
| Marriott Legal Limited | Other services | 2017 |
| Marriott Scaffolding Ltd | Construction | 2017 |
| Marruck Property Letting Agents Limited | Real estate | 2004 |
| Marsdenkeir Group Ltd | Wholesale & retail | 2023 |
| Marshall Arts Photography Limited | Extraterritorial | 2003 |
| Marshall Electrical System Ltd | Construction | 2014 |
| Marshalls Drone Services Ltd | Professional & scientific | 2023 |
| Marsim Limited | Real estate | 2013 |
| Marsty Limited | Real estate | 2023 |
| Martello Engineering and Management Ltd | Professional & scientific | 2021 |
| Martin Giles Property Group Ltd | Construction | 2026 |
| Martin Hudson Properties Ltd | Real estate | 2025 |
| Martin Robinson Carpentry Ltd | Construction | 2005 |
| Martins & Singh Paralegal Ltd | Professional & scientific | 2025 |
| Martins Singh Consultancy Limited | Professional & scientific | 2025 |
| Martins Singh Immigration Lawyers Limited | Professional & scientific | 2025 |
| Marvel B W Services Limited | Water & waste | 2025 |
| Marwezi Limited | Health & social care | 2017 |
| Mary Thomas Merchandiser Ltd | Professional & scientific | 2023 |
| Marydany Limited | Transport & logistics | 2018 |
| Mason Cleaning Contractors Ltd | Administrative & support | 2020 |
| Massage and Treatment Limited | Other services | 2023 |
| Massage Holistic Therapy Ltd | Health & social care | 2021 |
| Master Ropemakers (Trading) Limited | Manufacturing | 1991 |
| Master Ropemakers Ltd | Manufacturing | 2010 |
| Mastercraft Property Solutions Limited | Construction | 2012 |
| Masterflue Chimney Sweeps Limited | Construction | 2019 |
| Masters Distribution Ltd | Wholesale & retail | 2026 |
| Masters Knowles Developments Farnham Limited | Construction | 2021 |
| Masters Knowles Developments South East Limited | Construction | 2022 |
| Mastery Edge Limited | Professional & scientific | 2021 |
| Matked Limited | Health & social care | 2013 |
| Matthew Compton Limited | Construction | 2007 |
| Matthew David Limited | Extraterritorial | 2008 |
| Matthew David London Limited | Extraterritorial | 2008 |
| Matthew Paget Limited | Arts & recreation | 2015 |
| Matthew Peacock Associates Ltd | Professional & scientific | 2010 |
| Matthew Wilkes Wealth Management Limited | Professional & scientific | 2012 |
| Mavburgate Ltd | Construction | 2025 |
| Mavison Developments Ltd | Financial services | 2023 |
| Mavrck Ltd | Professional & scientific | 2026 |
| Mawtraining Solutions Ltd | Education | 2019 |
| MAX - Mobile Limited | Transport & logistics | 2012 |
| Maxim PR & Marketing Limited | Professional & scientific | 1999 |
| Maximo Life Ltd | Wholesale & retail | 2020 |
| MAY 27 Limited | Real estate | 2001 |
| MAY and Pearl Ltd | Administrative & support | 2025 |
| MAY Rose Developments Ltd | Real estate | 2017 |
| MAY Villa Music Limited | Professional & scientific | 2018 |
| Maybrick Property Ltd | Real estate | 2024 |
| Maybrooks Construction Limited | Construction | 2007 |
| Mayflower Spa Dorking Ltd | Health & social care | 2019 |
| Mayjve Limited | Wholesale & retail | 2008 |
| Mayjve Property & Investment Limited | Real estate | 2026 |
| Maynden Building Company Limited | Construction | 2024 |
| Mayoruk Property Investment Limited | Real estate | 2024 |
| Mazion Healthcare UK Limited | Health & social care | 2009 |
| MB Accounting Ltd | Professional & scientific | 2011 |
| MB Waterproofing and Construction Ltd | Construction | 2021 |
| MBE Property and Investments Limited | Real estate | 2025 |
| MBE Services Holdings Limited | Financial services | 2025 |
| MC Beauty & Aesthetics Ltd | Other services | 2019 |
| MC Fisheries Ltd | Professional & scientific | 2019 |
| MC Site Services Limited | Construction | 2025 |
| MC. Right Care Limited | Health & social care | 2019 |
| Mcac Kent Ltd | Construction | 2026 |
| Mcbrownie Limited | Professional & scientific | 2018 |
| Mccartney Healthcare Associates Limited | Professional & scientific | 2015 |
| Mchardy Property Holdings Ltd | Financial services | 2012 |
| Mckone Media Limited | Education | 2018 |
| MCL (Kent) Ltd. | Construction | 1978 |
| Mclaren Crafted Union Limited | Manufacturing | 2025 |
| MCM Recruitment Limited | Construction | 2014 |
| Mcobe Ventures Ltd | Hospitality | 2020 |