| LUX Lucis Limited | Administrative & support | 2011 |
| LUX PCO Limited | Administrative & support | 2019 |
| Luxe Academy London Limited | Other services | 2025 |
| LV Contract Services Ltd | Other services | 2018 |
| LVJ Partner Group Ltd | Professional & scientific | 2024 |
| LVS Services Limited | Transport & logistics | 2019 |
| Lwc-Luxury Watch Company Ltd | Wholesale & retail | 2019 |
| Lx-Physio Ltd | Other services | 2020 |
| LY Consulting Services Ltd | Information & communication | 2022 |
| Lyana UK Limited | Other services | 2025 |
| Lynne Hills Occupational Therapy Ltd | Health & social care | 2026 |
| Lyon Legal Services Limited | Professional & scientific | 2022 |
| LZ Sons Limited | Construction | 2017 |
| LZZ Foods Stratford Limited | Hospitality | 2025 |
| M &E Trading Ltd | Wholesale & retail | 2026 |
| M a a M Ventures Limited | Transport & logistics | 2016 |
| M Estates London Building & Construction Ltd | Construction | 2024 |
| M Estates London Investments Ltd | Real estate | 2021 |
| M Estates London Ltd | Households | 2019 |
| M Gorman Electrical Installations Ltd | Construction | 2012 |
| M H Barber Limited | Other services | 2023 |
| M J B Developments Limited | Real estate | 1974 |
| M J Smart Limited | Construction | 2019 |
| M K Star Private Ltd | Wholesale & retail | 2022 |
| M Land & Property Ltd | Real estate | 2026 |
| M Maxted Ltd | Extraterritorial | 2024 |
| M Mcgrath Ltd | Extraterritorial | 2025 |
| M Mushtaq Limited | Health & social care | 2012 |
| M Project Consultancy Ltd | Information & communication | 2021 |
| M W Restructuring Limited | Real estate | 2013 |
| M Whinney Holdings Limited | Administrative & support | 2018 |
| M&B Property Group Limited | Real estate | 2025 |
| M&Co Accounting Services Ltd | Professional & scientific | 2019 |
| M&L Properties UK Limited | Real estate | 2004 |
| M&S Contracting Services Limited | Construction | 2012 |
| M&S Karim Ltd | Financial services | 2023 |
| M&S Karim Properties Ltd | Real estate | 2023 |
| M-Fit Fitness & Nutrition Ltd | Arts & recreation | 2020 |
| M. Farmers Markets Limited | Administrative & support | 2004 |
| M4 Singh Ltd | Construction | 2023 |
| MA Hire Ltd | Construction | 2025 |
| MA Sky Limited | Construction | 2025 |
| Maanee Limited | Health & social care | 2014 |
| MAC Alley Limited | Manufacturing | 2014 |
| MAC Associated Companies Limited | Wholesale & retail | 1996 |
| Macanta Investments Limited | Financial services | 2024 |
| Mackenroad Management Company Limited | Households | 1986 |
| Macleod Mechanical Services Ltd | Construction | 2016 |
| Madden-Mclaren Limited | Health & social care | 2024 |
| Madeava Limited | Other services | 2022 |
| Madeyoulook Limited | Professional & scientific | 2000 |
| Madhu Tiruveedhula Ortho Ltd | Health & social care | 2018 |
| Madlani Projects Ltd | Construction | 2022 |
| Magda Dana Ltd | Wholesale & retail | 2019 |
| Mage Limited | Real estate | 2020 |
| Magebrew Ltd | Information & communication | 2021 |
| Magenta Stem Limited | Administrative & support | 2024 |
| Magic Bubblelloons Ltd | Wholesale & retail | 2020 |
| Magneto Geometric Applications Limited | Wholesale & retail | 2003 |
| Magnoquest Limited | Real estate | 1973 |
| Maidencross Limited | Administrative & support | 2013 |
| Maids of Mayfair Limited | Extraterritorial | 2025 |
| Maidstone Builders Merchants Ltd | Wholesale & retail | 2016 |
| Maikak Limited | Public administration | 2025 |
| Mainkey Ltd | Construction | 2022 |
| Maintron Property Co. Limited | Households | 1984 |
| Mairi MAC Limited | Information & communication | 2013 |
| Maison D'Afie Ltd | Wholesale & retail | 2009 |
| Maison Manuel Ltd | Hospitality | 2019 |
| Maison Mercer Ltd | Administrative & support | 2021 |
| Maizon Events Ltd | Administrative & support | 2024 |
| Majoyklean Ltd | Manufacturing | 2026 |
| MAK Boots & Garments Limited | Manufacturing | 2026 |
| MAK Consulting Services Limited | Administrative & support | 2024 |
| MAK Healthcare Limited | Health & social care | 2012 |
| Make UP by Barbara Ayisi Limited | Other services | 2021 |
| Makesflow Ltd | Health & social care | 2023 |
| Makhaira Consulting Ltd | Professional & scientific | 2022 |
| Making Medics Ltd | Education | 2016 |
| Makissi Limited | Wholesale & retail | 2020 |
| Makoko International Limited | Hospitality | 2025 |
| Malabaarii Ltd | Hospitality | 2023 |
| Malachi Care Limited | Health & social care | 2023 |
| Malankara Limited | Construction | 2025 |
| Malcolm Building Services Limited | Construction | 2017 |
| Malden Consultants Limited | Professional & scientific | 2025 |
| Malekos Estates Commercial Ltd | Real estate | 2014 |
| Malekos Productions Ltd | Information & communication | 2023 |
| Malik Consultancy Associated Ltd | Real estate | 2022 |
| Maloney Group Limited | Construction | 2023 |
| Mama Sanctuary Ltd | Health & social care | 2023 |
| MAN Made Perfection Limited | Construction | 2026 |
| Mana Security Limited | Administrative & support | 2021 |
| Management Revisions Limited | Professional & scientific | 1980 |
| Manak Lawyers Limited | Professional & scientific | 2015 |
| Manak Transport Ltd | Transport & logistics | 2024 |
| Manatti Enterprise Limited | Other services | 2017 |
| Manchanda Estates Limited | Real estate | 2025 |
| Mango IT Ltd | Information & communication | 2010 |
| Mango Loco Limited | Manufacturing | 2026 |