| Mannering Projects Limited | Construction | 2014 |
| Manuva Ltd | Information & communication | 2019 |
| Manyu & Co Properties Ltd | Real estate | 2022 |
| Mapconstruct Limited | Information & communication | 2005 |
| Marcus James Office Solutions Limited | Wholesale & retail | 2021 |
| Mareth Holdings LLP | | 2021 |
| Marine House Management Company Limited | Households | 2016 |
| Marinus Development Ltd | Real estate | 2020 |
| Marketplace Offers Ltd | Wholesale & retail | 2019 |
| Marq One Studios Ltd | Professional & scientific | 2024 |
| Martell French Polishing Limited | Other services | 2012 |
| Martin Balmer Limited | Professional & scientific | 2000 |
| Martin Roberts Enterprises Limited | Real estate | 2008 |
| Martin Towell Construction Limited | Construction | 2001 |
| Masala Bay 01 Ltd | Hospitality | 2025 |
| Masande Limited | Professional & scientific | 2010 |
| MASTERMIND2.0 Ltd | Health & social care | 2015 |
| Mather & SON Farms Limited | Agriculture & fishing | 2024 |
| Mathers & Hirst Whitstable Ltd | Wholesale & retail | 2013 |
| Matlox Joinery Ltd | Manufacturing | 2026 |
| Matt Kemp Projects Limited | Professional & scientific | 2026 |
| Matthew GUY Consultancy Ltd | Construction | 2024 |
| Maxton Prime Limited | Wholesale & retail | 2020 |
| Maya's Community C.I.C. | Health & social care | 2022 |
| Mayabagul Ltd | Other services | 2022 |
| Mayadany Business Ltd | Wholesale & retail | 2022 |
| Mayes Partnership LLP | | 2020 |
| Mayland Consult Ltd | Professional & scientific | 2024 |
| Maynard Electrical Limited | Construction | 2005 |
| Mbdexteriorcleaning Ltd | Administrative & support | 2026 |
| MBJ Business Services Ltd | Administrative & support | 2018 |
| MBJ Property Services Ltd | Real estate | 2022 |
| MBS Concrete Pumping Limited | Manufacturing | 2015 |
| MBS Transport Kent Ltd | Transport & logistics | 2022 |
| Mcdarby Developments Limited | Real estate | 2003 |
| Mcgrath Fixing Ltd | Construction | 2015 |
| Mckenzie Developments (Kent) Ltd | Manufacturing | 2019 |
| Mcmillan Chang Limited | Real estate | 2021 |
| MD Pension Limited | Real estate | 2023 |
| MD Transport Consultancy Ltd | Transport & logistics | 2025 |
| MDP Contractors Ltd | Construction | 2018 |
| Medcorp Limited | Financial services | 2005 |
| Medi's London Ltd | Hospitality | 2025 |
| Media Consortium Limited | Information & communication | 2007 |
| Medsurgico Limited | Wholesale & retail | 2023 |
| MEG in Motion Ltd | Information & communication | 2019 |
| Melville Marine Limited | Transport & logistics | 2011 |
| Mend London Limited | Professional & scientific | 2010 |
| MEP Project Management Solutions Ltd | Professional & scientific | 2026 |
| MER Taxi Limited | Transport & logistics | 2026 |
| Mercano Limited | Real estate | 2016 |
| Meridian Box Sash Windows Ltd | Construction | 2015 |
| Merique Limited | Wholesale & retail | 2023 |
| Merkaj Property Ltd | Real estate | 2022 |
| Metis Advisory International Ltd | Professional & scientific | 2025 |
| MGW Property Ltd | Real estate | 2015 |
| Michael a Turner Ltd | Professional & scientific | 2023 |
| Micik Ltd | Hospitality | 2025 |
| Mickleburgh Apartments (Herne Bay) Limited | Households | 1990 |
| Middleton Roofing Limited | Construction | 2025 |
| Mididol Limited | Construction | 1988 |
| Mightyfinethings Limited | Manufacturing | 2014 |
| Mijlof Tile Consultants Ltd | Professional & scientific | 2025 |
| Millhatch Properties Limited | Real estate | 2012 |
| MIM MIM Limited | Information & communication | 2014 |
| Ming Garden (Herne Bay) Limited | Hospitality | 2015 |
| Mini Cars Today Ltd | Wholesale & retail | 2021 |
| Minimal Viable Launch Ltd | Professional & scientific | 2021 |
| Miri Properties Limited | Real estate | 2025 |
| Mitcham Building Supplies Ltd | Wholesale & retail | 2012 |
| Mitchell & Cleary Ltd | Public administration | 2019 |
| Mixx LAB Limited | Arts & recreation | 2026 |
| Mlglazing Ltd | Construction | 2025 |
| MLJ Qualitech Ltd | Information & communication | 2023 |
| Mmsck Ltd | Wholesale & retail | 2025 |
| MO Ismail Ltd | Health & social care | 2023 |
| Mobile LAB Ltd | Professional & scientific | 2013 |
| Modern Blinds & Shutters Ltd | Construction | 2018 |
| Modox Ltd | Construction | 2011 |
| Mokacino Productions Limited | Other services | 2017 |
| Moling Services South East Limited | Administrative & support | 2010 |
| Monad Holdings Ltd | Wholesale & retail | 2024 |
| Monkey Solutions Limited | Transport & logistics | 2023 |
| Montford Bay Ltd | Professional & scientific | 2020 |
| Moonhill Homes Ltd | Health & social care | 2024 |
| Moonstone Productions Limited | Extraterritorial | 1999 |
| Morgan and Smith Construction Ltd | Construction | 2017 |
| Morgana Logistics Ltd | Transport & logistics | 2024 |
| Mortimer & East Street Management Company Limited | Households | 2013 |
| Mortonstock Limited | Wholesale & retail | 2025 |
| Motivated & Competent Training Limited | Information & communication | 2007 |
| Motor Breaker Limited | Information & communication | 2013 |
| Motortech (Kent) Limited | Wholesale & retail | 2009 |
| Mount View Electrical Ltd | Construction | 2018 |
| Moxshire Property Investment Company Ltd | Real estate | 2019 |
| MPA Consultancy Ltd | Professional & scientific | 2016 |
| MR Madd Ltd | Transport & logistics | 2018 |
| MR Padfield’S Pickles Ltd | Manufacturing | 2021 |
| MR Simm's Ramsgate Ltd | Wholesale & retail | 2019 |
| MS Atlantic Ltd | Transport & logistics | 2020 |