| Medica GP Limited | Health & social care | 2022 |
| Medica Market Access Limited | Professional & scientific | 2011 |
| Medical Family Finance Ltd | Financial services | 2013 |
| Medical-Eagle (UK) Limited | Health & social care | 2015 |
| Medila Limited | Hospitality | 2017 |
| Medisci Ltd | Health & social care | 2018 |
| Medway Management (Tonbridge) Limited | Households | 2000 |
| Megaview Limited | | 1983 |
| Melandy Limited | Real estate | 2013 |
| Melanie Envy London Limited | Administrative & support | 2015 |
| Melvyn Davies & Co Limited | Professional & scientific | 2008 |
| Memoraid Limited | Information & communication | 2002 |
| Mercury Global Management Ltd | Professional & scientific | 2025 |
| Meridian Maintenance Ltd | Construction | 2024 |
| Merlin Commercial Properties Ltd | Real estate | 2019 |
| Merrywell Systems Ltd | Information & communication | 2007 |
| Mesher & Stevens Limited | Professional & scientific | 2005 |
| Mesmerising Aesthetics Ltd | Other services | 2023 |
| Messiah and EVE Limited | Wholesale & retail | 2020 |
| Messinian Services Ltd | Professional & scientific | 2018 |
| Metta Investment Ltd | Financial services | 2025 |
| Mettra Limited | Arts & recreation | 2015 |
| Mews Medical LLP | | 2025 |
| MEX Developments Ltd | Construction | 2025 |
| MEX Structures Ltd | Professional & scientific | 2022 |
| Mezzpart Holdings Limited | Financial services | 2020 |
| MF Design Solutions Ltd | Professional & scientific | 2024 |
| MFA (Kent) Ltd | Arts & recreation | 2020 |
| MFF London Ltd | Financial services | 2013 |
| MFG Fitness Ltd | Arts & recreation | 2026 |
| MG Plastic Surgery Ltd | Health & social care | 2018 |
| Mggk Ltd | Other services | 2020 |
| MGN Repairs Management Limited | Construction | 2015 |
| Mhengineering Ltd | Professional & scientific | 2026 |
| MI Imaging Limited | Health & social care | 2021 |
| Michael Joyce Civil Engineering Contractor Limited | Wholesale & retail | 1997 |
| Michael Macdonald Construction Limited | Construction | 2013 |
| Michael Quigley Plumbing and Heating Limited | Construction | 2018 |
| Michael's Co. Ltd Limited | Wholesale & retail | 2025 |
| Michaels Auto Trading Limited | Extraterritorial | 2023 |
| Micks Carpentry & Building Contracts Ltd | Construction | 2015 |
| Microtech Ceramics Limited | Professional & scientific | 2013 |
| Midas Kitchens Ltd | Manufacturing | 2005 |
| Midlife Group Ltd | Wholesale & retail | 2026 |
| Mike Renton Production Accounting Limited | Administrative & support | 2022 |
| Milagros Property Ltd | Real estate | 2018 |
| Milbrooke Holdings Limited | Financial services | 2020 |
| Milbrooke Limited | Construction | 2012 |
| Military in Motion Limited | Education | 2019 |
| Mill Advisory Limited | Administrative & support | 2025 |
| Mill Crescent Holdings Limited | Financial services | 2012 |
| Mill Garage Hildenborough LLP | | 2015 |
| Millar Scott Consultants Ltd | Health & social care | 2022 |
| Millennium Trading Ltd | Wholesale & retail | 2021 |
| Miller Architect and Associates Limited | Professional & scientific | 2011 |
| Millican Marketing Limited | Professional & scientific | 2024 |
| Millies Public House Limited | Hospitality | 2025 |
| Millside Mews Residents Association Limited | Households | 1999 |
| Millsons Vending Limited | Hospitality | 2003 |
| Mind Solutions (UK) Limited | Administrative & support | 2014 |
| Mind's EYE Design Limited | Administrative & support | 2002 |
| Mindfulness in Schools Project | Education | 2009 |
| Mineirinho Brazilian Food Ltd | Manufacturing | 2020 |
| Minima Energy Limited | Construction | 2016 |
| Minima Sliding Limited | Construction | 2015 |
| Minkford Consulting Limited | Real estate | 2010 |
| Minkford Holdings Limited | Real estate | 2010 |
| Minkley and Jacobs Limited | Wholesale & retail | 2017 |
| Mirahurst Solutions Limited | Construction | 2011 |
| Miselford Consulting Limited | Real estate | 2010 |
| Miselford Holdings Limited | Real estate | 2010 |
| Miss Mardle's Companions Ltd | Health & social care | 2022 |
| Mitchell Marine Limited | Manufacturing | 2026 |
| Mitchells Printing Limited | Manufacturing | 1970 |
| MJC Lettings Ltd | Real estate | 2025 |
| MJG Electrical Controls Limited | Manufacturing | 2011 |
| MJH Data Recovery Limited | Information & communication | 2008 |
| MJL Enterprises Limited | Wholesale & retail | 2012 |
| MKH Properties Limited | Real estate | 2009 |
| MLCA3 Consulting Limited | Information & communication | 2018 |
| MLL Consulting Limited | Professional & scientific | 2016 |
| MLV Construction Limited | Construction | 2015 |
| MM Building Surveyors Ltd | Professional & scientific | 2021 |
| MM Trading & Investment Ltd | Financial services | 2021 |
| Mmlv Group Limited | Real estate | 2020 |
| Mmor Consulting Ltd | Information & communication | 2017 |
| Mmor Love Limited | Real estate | 2025 |
| MNB Training Academy Limited | Education | 2018 |
| Mnel Transport Ltd | Transport & logistics | 2015 |
| Mnrexotics Ltd | Professional & scientific | 2024 |
| MNT Retail Limited | Wholesale & retail | 2024 |
| Moatlands Service Company Limited | Households | 2023 |
| Mobivape Kent Ltd | Wholesale & retail | 2021 |
| Mochafella Leisure Ltd | Arts & recreation | 2017 |
| Modesty Motors Limited | Wholesale & retail | 2014 |
| Modular One Estate Ltd | Construction | 2016 |
| Modze Trading Company Ltd | Wholesale & retail | 2020 |
| Mohini Film-Kraft Limited | Information & communication | 2020 |
| Molecular Oncology Limited | Health & social care | 2013 |
| Molecule Holdings Limited | Financial services | 2024 |