| Lyncs Media Limited | Information & communication | 2014 |
| Lynzo Ltd | Information & communication | 2024 |
| Lyrastar Limited | Transport & logistics | 2001 |
| Lyria Ltd | Administrative & support | 2012 |
| Lytchgate Limited | Real estate | 1952 |
| Lythouse Limited | Professional & scientific | 2022 |
| M & D Consultants (Kent) Limited | Administrative & support | 2015 |
| M & L Scaffold (South East) Limited | Construction | 2017 |
| M & M Monitoring Services Ltd | Professional & scientific | 2010 |
| M & S Grass Cutting Limited | Agriculture & fishing | 2015 |
| M & S Investments (U.K.) Limited | Real estate | 1998 |
| M & Z Property Services Ltd | Real estate | 2024 |
| M a Construction and Landscaping Ltd | Construction | 2025 |
| M C a Fixings Limited | Manufacturing | 2013 |
| M C S C Restaurants Limited | Hospitality | 2021 |
| M Davis Ltd | Construction | 2021 |
| M Ezeike Limited | Professional & scientific | 2023 |
| M H Motorcycles Ltd | Wholesale & retail | 2024 |
| M I a (Atm's) Limited | Professional & scientific | 2004 |
| M L Projects Limited | Professional & scientific | 2001 |
| M P Bookkeeping Services Ltd | Professional & scientific | 2018 |
| M Power Limited | Health & social care | 1995 |
| M R Electrical & Property Services Limited | Construction | 2013 |
| M Regulatory Consultancy Ltd | Professional & scientific | 2019 |
| M&A Build Ltd | Construction | 2025 |
| M&A Fortunes Ltd | Information & communication | 2005 |
| M&A Studio Limited | Hospitality | 2025 |
| M&C Engineering Group Limited | Administrative & support | 2023 |
| M&N Technology Solutions Limited | Information & communication | 2024 |
| M&Y Engineering Limited | Professional & scientific | 2019 |
| M. Dolovich Ltd | Education | 2006 |
| M.A. Centre, UK | Health & social care | 2009 |
| M.D. Carvell Associates Ltd | Professional & scientific | 2018 |
| M.D.A Refurbishment Limited | Construction | 2016 |
| M.M. Morris Builder Limited | Construction | 2015 |
| M24 Consulting Ltd | Professional & scientific | 2025 |
| M31 Group Ltd | Professional & scientific | 2022 |
| M4 Gibbs Ltd | Administrative & support | 2019 |
| MA Divane Contractors Limited | Construction | 2015 |
| MA Private Limited | Wholesale & retail | 2025 |
| Ma-Zez Ltd | Extraterritorial | 2025 |
| Maam Management Limited | Real estate | 2014 |
| Mabcom Limited | Administrative & support | 2021 |
| Mabel Properties LLP | | 2016 |
| Mabini Limited | Construction | 2016 |
| MAC 3X3 Limited | Arts & recreation | 2025 |
| MAC Construction D&B Ltd | Construction | 2018 |
| MAC Fortune Consulting Ltd | Professional & scientific | 2024 |
| Macbuild Construction Ltd. | Construction | 2014 |
| Mace Financial Limited | Professional & scientific | 2014 |
| Mack & Candy Holdings Limited | Real estate | 2023 |
| Macka Property Investments Limited | Real estate | 2025 |
| Mackley Home Care Limited | Health & social care | 1999 |
| Macks Heating Limited | Construction | 2014 |
| Macoral Services Limited | Transport & logistics | 2023 |
| Macrm Ltd. | Information & communication | 2017 |
| Macrocare Ltd | Hospitality | 2023 |
| Macy Interiors Limited | Administrative & support | 2019 |
| MAD Diner Limited | Extraterritorial | 2018 |
| MAD Leap CIC | Agriculture & fishing | 2022 |
| MAD Money Ltd | Other services | 2025 |
| MAD Potato Studios Ltd. | Information & communication | 2021 |
| MAD Swaz Ltd | Information & communication | 2024 |
| Maddison Group Limited | Professional & scientific | 2002 |
| Made to Measure Woodwork Limited | Manufacturing | 2009 |
| MADE2BOX Ltd | Manufacturing | 2025 |
| Madhuwan Restaurant Ltd | Hospitality | 2018 |
| Madoonas Property Ltd | Real estate | 2026 |
| MAE Aesthetics Limited | Other services | 2020 |
| Mafssbeco Ltd | Other services | 2024 |
| Maghfir Lana Property Limited | Real estate | 2024 |
| Magic Mouth Ltd | Information & communication | 2025 |
| Magic Penpals Limited | Education | 2020 |
| Magic Scissors (Bromley) Ltd | Other services | 2017 |
| Magical Storage Limited | Extraterritorial | 2010 |
| Magiq Group Ltd | Wholesale & retail | 2023 |
| Magnify London Ltd | Extraterritorial | 2017 |
| Magp Ltd | Extraterritorial | 2026 |
| Magpie Dance | Arts & recreation | 1996 |
| Magpie Hall Lane Management Company Limited | Real estate | 1996 |
| Mahezi Ltd | Professional & scientific | 2025 |
| Mahsa Corporation Ltd | Extraterritorial | 2024 |
| MAI Hair Limited | Other services | 2021 |
| Maia Property Limited | Real estate | 2007 |
| Maia Yachting Limited | Extraterritorial | 2024 |
| Maid Solutions Ltd | Administrative & support | 2018 |
| MAID2CLEAN Dulwich Ltd | Administrative & support | 2011 |
| Mailninja Limited | Information & communication | 2013 |
| Maine Property Services Ltd | Construction | 2022 |
| Maintain Building and Construction Limited | Construction | 2021 |
| Maison Kreativ Limited | Professional & scientific | 2023 |
| Maitie Limited | Wholesale & retail | 2023 |
| Maitu Properties Limited | Real estate | 2018 |
| Majestic Luxury Limited | Manufacturing | 2021 |
| Major Realty Limited | Real estate | 2023 |
| Majoy International Limited | Administrative & support | 2019 |
| Majoy Property Investment Ltd | Real estate | 2022 |
| MAK Health Limited | Manufacturing | 2016 |
| MAK Manufacturing Ltd | Wholesale & retail | 2016 |
| MAK Robert Consultancy Limited | Administrative & support | 2012 |