| Marl Creative Limited | Other services | 2024 |
| Marlay Group Limited | Other services | 2020 |
| Marlborough Court Residents (Harrow) Limited | Households | 2006 |
| Marlborough Hill Tenants Company Limited | Administrative & support | 2014 |
| Marlene Kelly Consulting Ltd | Professional & scientific | 2026 |
| Marlo Antiques Limited | Wholesale & retail | 2025 |
| Marlor Limited | Arts & recreation | 2017 |
| Marlow & Marlow Limited | Real estate | 2020 |
| Marlowes Imperial Ltd | Real estate | 2025 |
| Marls Trading Limited | Manufacturing | 2016 |
| Marmaduke Medical Limited | Health & social care | 2021 |
| Marnham Property Limited | Real estate | 2022 |
| Marocwonder Ltd | Administrative & support | 2024 |
| Maroon Intl Trading Ltd | Wholesale & retail | 2025 |
| Maroon Mountain Limited | Hospitality | 2017 |
| Marose Jewels Ltd | Wholesale & retail | 2014 |
| Marric Bay Liner Ltd | Transport & logistics | 2020 |
| Marry Hill INT Ltd | Information & communication | 2024 |
| Mars Consulting (London) Limited | Information & communication | 2025 |
| Mars Restaurant Ltd | Hospitality | 2018 |
| Marsden Surveyors Limited | Professional & scientific | 2012 |
| Marseo Limited | Professional & scientific | 2023 |
| Marsh Court Limited | Real estate | 2025 |
| Marsh END Ltd | Health & social care | 2020 |
| Marsh Real Estate Holdings Ltd | Real estate | 2020 |
| Marshall House Management Company Limited | Real estate | 1987 |
| Marshall Property Investments Ltd | Real estate | 2018 |
| Marshbay Limited | Other services | 2016 |
| Marshcroft Energy Limited | Information & communication | 2010 |
| Marshcroft Farm Ltd | Real estate | 2020 |
| Marshom Solutions Limited | Information & communication | 2018 |
| Marsolier & Associates Limited | Professional & scientific | 2016 |
| Marstar Properties Ltd | Construction | 2021 |
| Marsus Consulting Ltd | Professional & scientific | 2022 |
| Mart Construction Ltd | Construction | 2017 |
| Martin Antonio Investments Ltd | Real estate | 2018 |
| Martin Brennan Auditing Services Ltd | Hospitality | 2017 |
| MARTIN3X Ltd | Construction | 2024 |
| Martplaza Ltd | Wholesale & retail | 2026 |
| Martworld Limited | Real estate | 1979 |
| Maru Estates Ltd | Real estate | 2024 |
| Marudhar Investments Ltd | Real estate | 2022 |
| Maruthanila Ltd. | Extraterritorial | 2004 |
| Maruti Apparel Limited | Construction | 2018 |
| Maruti Bites Ltd | Hospitality | 2026 |
| Maruti Catering Limited | Hospitality | 2025 |
| Maruti Deliveries Limited | Wholesale & retail | 2025 |
| Maruti Enterprise Limited | Real estate | 2021 |
| Maruti ENTERPRISE18 Ltd | Wholesale & retail | 2026 |
| Maruti Interiors Ltd | Construction | 2026 |
| Maruti Nandan Investments Limited | Real estate | 2020 |
| Maruti Nandan Private Limited | Wholesale & retail | 2025 |
| Maruti Nandan Properties Limited | Real estate | 2011 |
| Marv Investment Ltd | Real estate | 2017 |
| Marval Services Limited | Construction | 1987 |
| Marvasco Limited | Construction | 2018 |
| Marvel Life Sciences Limited | Administrative & support | 1999 |
| Marvellous Movers Limited | Water & waste | 2022 |
| Marvern Ltd | Professional & scientific | 2019 |
| Marvin Entertainment Limited | Arts & recreation | 2022 |
| Marvinn Commercial and Residential Construction UK Limited | Construction | 2022 |
| Marvinn Commercial and Residential Properties UK Limited | Real estate | 2022 |
| Marwa Zarif Ltd | Other services | 2020 |
| Marwaha Enterprises UK Limited | Education | 2010 |
| Marxaney Limited | Professional & scientific | 2012 |
| Mary Greenwell Limited | Professional & scientific | 1996 |
| Mary Helen Young Consulting Ltd | Professional & scientific | 2025 |
| Mary Holdings Ltd | Real estate | 2026 |
| Maryam Investment Ltd | Real estate | 2019 |
| Maryam TAJ UK Ltd | Wholesale & retail | 2024 |
| Marygold Care UK Ltd | Health & social care | 2012 |
| Maryland Enterprises INT Limited | Wholesale & retail | 2022 |
| Marylebone and Belgravia Developments Limited | Real estate | 2021 |
| Marylebone Investment Holdings Ltd | Financial services | 2023 |
| Marylebone Investments Ltd | Real estate | 2024 |
| Marylebone Medical Group Limited | Health & social care | 2013 |
| Maryo Transport Ltd | Transport & logistics | 2025 |
| Marz Medical Ltd | Health & social care | 2025 |
| Marzo London Limited | Administrative & support | 2015 |
| MAS London Holding Ltd | Real estate | 2026 |
| MAS Prats Limited | Real estate | 1975 |
| Masa Elite Ltd | Hospitality | 2024 |
| Masa Star Holding Ltd | Financial services | 2025 |
| Masala & Coal Ltd | Hospitality | 2022 |
| Masala Caterers Limited | Hospitality | 2016 |
| Masala Odyssey Ltd | Hospitality | 2024 |
| Masala Vibes Productions Ltd | Arts & recreation | 2025 |
| Maseed Rice Ltd | Wholesale & retail | 2024 |
| Mash Homes Limited | Real estate | 2024 |
| Mash UP! Productions Limited | Other services | 2014 |
| Mashal Charity Limited | Education | 2025 |
| MASI58 Ltd | Hospitality | 2025 |
| Maskatiya UK Limited | Wholesale & retail | 2020 |
| Maskho Limited | Manufacturing | 2012 |
| Masks Fleet Ltd | Hospitality | 2023 |
| Masks Hospitality Limited | Hospitality | 2019 |
| Masks Investments Limited | Real estate | 2024 |
| Masl Wealth Management Limited | Financial services | 2016 |
| Maslak Ltd | Information & communication | 2011 |
| Mason London Ltd | Information & communication | 2022 |