| Lunar Marine Trading Limited | Other services | 2018 |
| Lung Force Ltd | Wholesale & retail | 2025 |
| LUS3 Ltd | Wholesale & retail | 2024 |
| Lush Fruit Limited | Wholesale & retail | 2023 |
| Lush GEM Ltd | Administrative & support | 2024 |
| Luther Properties Limited | Real estate | 2024 |
| Luvono Ltd | Health & social care | 2016 |
| Luxadom Ltd | Wholesale & retail | 2025 |
| Luxcean Limited | Real estate | 2025 |
| Luxe Catering Group Ltd | Hospitality | 2021 |
| Luxe Nail Boutique Ltd | Other services | 2025 |
| Luxehem Ltd | Wholesale & retail | 2023 |
| Luxentiaco Ltd | Wholesale & retail | 2025 |
| Luxury Commerce Group Ltd | Wholesale & retail | 2025 |
| LYD U'S Miracle Cleaning & Clearing Services Ltd | Administrative & support | 2019 |
| Lyngen Limited | Manufacturing | 2001 |
| Lyntem Limited | Health & social care | 2024 |
| Lyon and SON Contracts Limited | Construction | 2022 |
| Lyons Footwear (Great Britain) Limited | | 1984 |
| Lyons Heavy Haulage Limited | Transport & logistics | 2007 |
| Lyte Pro Medics Ltd | Health & social care | 2025 |
| M & a Property Investments Limited | Real estate | 2007 |
| M & D Building Contractors Limited | Construction | 2003 |
| M & D London Ltd | Real estate | 2023 |
| M & I Direct Investment Ltd | Real estate | 2022 |
| M & J Harding LLP | | 2006 |
| M & K Consulting Limited | Professional & scientific | 2009 |
| M & M Maintenance Limited | Construction | 2006 |
| M & P Accountancy Services Limited | Professional & scientific | 1998 |
| M a Salam and Sons Limited | Real estate | 2024 |
| M Anderson Developments Limited | Real estate | 2005 |
| M B Decorating Ltd | Construction | 2003 |
| M B Parker Builders Limited | Construction | 2003 |
| M Croxall Limited | Construction | 2007 |
| M Donovan Ltd | Construction | 2007 |
| M Faisal Ltd | Wholesale & retail | 2025 |
| M Fitzgerald Electrical Services Limited | Manufacturing | 2025 |
| M G M Services Limited | Administrative & support | 1994 |
| M Greene Services Ltd | Construction | 2026 |
| M Hudd Flooring Services Limited | Construction | 2006 |
| M J Automotive Limited | Professional & scientific | 2002 |
| M K Associates Limited | Construction | 1993 |
| M K Contracts Ltd | Construction | 1996 |
| M King & Sons Ltd | Construction | 2005 |
| M London Construction Ltd | Construction | 2021 |
| M M a Education Limited | Information & communication | 2001 |
| M S & C Property Limited | Real estate | 2007 |
| M S Chemists Limited | Wholesale & retail | 2002 |
| M Webb Building Solutions Ltd | Construction | 2018 |
| M Z Designs Ltd | Real estate | 2026 |
| M&D Build Ltd | Construction | 2018 |
| M&F Turkish Barber Ltd | Other services | 2024 |
| M&L Bunney Limited | Professional & scientific | 2002 |
| M&L Fencing and Landscaping Ltd | Administrative & support | 2019 |
| M&T Talo Limited | Real estate | 2024 |
| M. & J. Spindley Limited | Construction | 1987 |
| M. & M. Associates (Buckhurst Hill) Limited | | 1979 |
| M. a. Skinner (Building Contractor) Limited | Construction | 2007 |
| M. Bareham (Glass Merchants) Limited | Wholesale & retail | 1973 |
| M. Picassini Limited | Construction | 2018 |
| M. Pierce Partnership Limited | Professional & scientific | 1990 |
| M. Shuttlewood Ltd | Construction | 2003 |
| M.A. Kennedy Limited | Transport & logistics | 2003 |
| M.A.S. Futures Limited | Extraterritorial | 1985 |
| M.B. Power Services (Essex) Ltd | Construction | 2000 |
| M.B. Power Services Limited | | 1972 |
| M.C. and S. Limited | Wholesale & retail | 2005 |
| M.C. Leigh Services Limited | Transport & logistics | 2005 |
| M.F.U Ltd | Administrative & support | 2010 |
| M.J. Little (Marine Engineers) Limited | | 1974 |
| M.J.B. Thermal Limited | Construction | 2000 |
| M.R.M Mechanical & Construction Services Limited | Construction | 2017 |
| M.S. Beamish Holdings Limited | | 1988 |
| MA Bakers Limited | Wholesale & retail | 1988 |
| MA Consulco Ltd | Information & communication | 2019 |
| MA Rafi Management Ltd | Households | 2025 |
| MA Traders London Ltd | Hospitality | 2019 |
| MA Trading (Grays) Ltd | Manufacturing | 2023 |
| MA. DEV. Limited | Real estate | 1998 |
| Maariyah Hairstylist Ltd | Other services | 2019 |
| Mabel Leisure Limited | Professional & scientific | 2019 |
| Mabs Trade and Consultancy Ltd | Wholesale & retail | 2022 |
| MAC Automotive Components Limited | Wholesale & retail | 2002 |
| Mac's Flooring Limited | Construction | 2003 |
| Macalle & Sons Limited | Wholesale & retail | 2023 |
| Machinery Users' Association(Incorporated)(The) | Professional & scientific | 1905 |
| Mackenross Limited | Wholesale & retail | 2002 |
| Macmillan Estate Planning Limited | Professional & scientific | 2015 |
| Macmillan Magic Limited | Wholesale & retail | 2007 |
| Macroprime Limited | Arts & recreation | 1992 |
| Macrowise Limited | Information & communication | 1996 |
| MAD About Theatre Company Limited | Arts & recreation | 2007 |
| Maddox FA Limited | Wholesale & retail | 2015 |
| Made by Bantu Ltd | Wholesale & retail | 2020 |
| Made by Coopers Apothecary Ltd | Wholesale & retail | 2017 |
| Made Investment Ltd | Real estate | 2024 |
| Made Simple Properties Ltd | Real estate | 2024 |
| Madls Fruits and VEG Ltd | Wholesale & retail | 2026 |
| Madzi Limited | Hospitality | 2023 |
| Magi Builders Limited | Construction | 2024 |