| Martingale Property Limited | Real estate | 2023 |
| Martinici Building Services Ltd | Construction | 2024 |
| Martlesham Hand Car Wash Ltd | Other services | 2018 |
| Martoj Solutions Ltd | Professional & scientific | 2024 |
| Marufu Investments Ltd | Health & social care | 2012 |
| Marvellous Healthcare Services Limited | Health & social care | 2021 |
| Maryamina Properties 2 Limited | Real estate | 2024 |
| Maryamina Properties 3 Limited | Real estate | 2025 |
| Maryamina Properties Limited | Real estate | 2020 |
| Maryams London Limited | Wholesale & retail | 2025 |
| Marybelle Limited | Real estate | 2015 |
| Marymartinb Ltd | Other services | 2018 |
| Maryo House Ltd | Hospitality | 2023 |
| Masela Builders Ltd | Construction | 2025 |
| Masela Catering Ltd | Hospitality | 2023 |
| Mask Tech Global Ltd | Wholesale & retail | 2025 |
| Massbe Ltd | Health & social care | 2024 |
| Master Autos Ltd | Wholesale & retail | 2022 |
| Master Care Services Ltd | Health & social care | 2024 |
| Master Mart Ltd | Wholesale & retail | 2024 |
| Masters Blueprint Property Services Ltd | Financial services | 2026 |
| Matash FRY Limited | Hospitality | 2023 |
| Mathbeecom Limited | Wholesale & retail | 2017 |
| Mather Engineering Limited | Manufacturing | 1973 |
| Mather Holdings Group Ltd | Financial services | 2024 |
| Mather Systems Ltd | Professional & scientific | 2026 |
| MATI11 Ltd | Construction | 2022 |
| Matpal Properties Ltd | Real estate | 2023 |
| Matrix Spectrum Technology Limited | Information & communication | 2024 |
| Matrixx Designs Ltd | Other services | 2025 |
| Matteo Sprinkler Systems Ltd | Public administration | 2024 |
| Mattex Ltd | Wholesale & retail | 2008 |
| Mattloko Limited | Administrative & support | 2022 |
| Mauya Limited | Hospitality | 2024 |
| Mavita Ltd | Wholesale & retail | 2026 |
| Mavrik Musk (London) Ltd | Wholesale & retail | 2024 |
| MAX Pharmacare Limited | Information & communication | 2017 |
| MAX Therm Solutions Ltd | Construction | 2025 |
| Maxispan Limited | Financial services | 1988 |
| Maxsum Intellect Ltd | Wholesale & retail | 2017 |
| Maxtrading Limited | Wholesale & retail | 2019 |
| Maya Health Ltd | Health & social care | 2015 |
| Maya Residence Limited | Real estate | 2017 |
| Mayah & Co Consulting Limited | Professional & scientific | 2014 |
| Mayah and Co Real Estate Limited | Real estate | 2023 |
| Mayas Fashion Limited | Wholesale & retail | 2024 |
| Maybury Estates Ltd | Real estate | 2022 |
| Mayesbrooks Limited | Real estate | 2024 |
| Mayfair Butler Small Works Ltd | Construction | 2020 |
| Mayfair Devolpers Ltd | Households | 2025 |
| Mayflower Property Development Limited | Real estate | 2023 |
| Mayouf & Daughter Ltd | Wholesale & retail | 2026 |
| MAZ Designs Limited | Professional & scientific | 2017 |
| MAZ Designs Properties Limited | Real estate | 2022 |
| Mazco Limited | Wholesale & retail | 2024 |
| Maze Architecture Ltd | Professional & scientific | 2023 |
| Mazhar Iqbal Properties Ltd | Real estate | 2025 |
| MB Academy CIC | Manufacturing | 2025 |
| MB Deen Limited | Construction | 2022 |
| MB Educational Consultancy Limited | Other services | 2016 |
| MB Expert Build Solutions Ltd | Construction | 2026 |
| MB Global Services Limited | Professional & scientific | 2026 |
| MBG25 Ltd | Manufacturing | 2025 |
| Mbinldn Ltd | Wholesale & retail | 2026 |
| MBM Automation Ltd | Information & communication | 2025 |
| Mboun's Family Limited | Health & social care | 2019 |
| Mbsuppliers Ltd | Wholesale & retail | 2021 |
| Mc&Son Limited | Arts & recreation | 2016 |
| Mcc-Millano UK Ltd | Construction | 2018 |
| Mcee Limited | Construction | 2022 |
| Mcee Property Ltd | Real estate | 2024 |
| Mckenna & Sons Holdings Limited | Real estate | 2025 |
| Mckinley Accountants Ltd | Professional & scientific | 2026 |
| Mctrade Force Ltd | Construction | 2024 |
| Mcvnet Ltd | Construction | 2021 |
| MD Business Development & Consultancy Ltd | Professional & scientific | 2015 |
| MD Contractors Facades Solutions Ltd | Construction | 2016 |
| MD Kiddies Solution UK Ltd | Health & social care | 2025 |
| MD Laica Construction Ltd | Construction | 2018 |
| Mdecraft Ltd | Construction | 2026 |
| Mdevi Ltd | Wholesale & retail | 2026 |
| Mdhb-Services Ltd | Construction | 2023 |
| MDM Drylining Limited | Construction | 2024 |
| MDM UK Global Ltd | Construction | 2025 |
| Mead Creator Network Ltd | Professional & scientific | 2026 |
| Mecha Car Parts Ltd | Wholesale & retail | 2025 |
| Medall Healthcare Ltd | Administrative & support | 2020 |
| Media Mojos Ltd | Information & communication | 2023 |
| Media Script Limited | Information & communication | 2019 |
| Media Shieldz Ltd | Wholesale & retail | 2018 |
| Media Spot Ltd | Professional & scientific | 2017 |
| Mediacrowd Ltd | Information & communication | 2025 |
| Mediatrix Health Care Services Ltd | Health & social care | 2018 |
| Medical Global Logistics Limited | Financial services | 2024 |
| Mediplus Healthcare Ltd | Health & social care | 2017 |
| Mediview Diagnostic Ltd | Health & social care | 2014 |
| Medtax Advisors Ltd | Professional & scientific | 2021 |
| Medworld Healthcare Ltd | Health & social care | 2022 |
| Meem Packaging Limited | Wholesale & retail | 2025 |
| Meet Eearly Limited | Hospitality | 2025 |