| Maple Court (Gerrards Cross) Residents Limited | Households | 1995 |
| Maple Rise Management Company Limited | Households | 2024 |
| Maren Limited | Extraterritorial | 2002 |
| Marigold Charms Limited | Wholesale & retail | 2019 |
| Mark Alexander Homes Limited | Real estate | 2016 |
| Market Place Management Company Limited | Households | 1988 |
| Marlen 54 Limited | Real estate | 2020 |
| Marlow Glazing Limited | Construction | 2011 |
| Marlow SA Property 2021 4 Ltd | Real estate | 2021 |
| Marlow SA Property 2022 1 Ltd | Real estate | 2021 |
| Marlow SA Property 2022 2 Ltd | Real estate | 2021 |
| Marlow SA Property 2023 1 Ltd | Real estate | 2023 |
| Marlow SA Property Freeholds 2021 Ltd | Households | 2021 |
| Marnie's Coffee Ltd | Hospitality | 2025 |
| Marsh Mill Residents Company Limited | Households | 1976 |
| Martin Core Consulting Ltd. | Information & communication | 1998 |
| Marula Partners Limited | Professional & scientific | 2024 |
| Mary Homer Ltd | Professional & scientific | 2024 |
| Masonic Travel Limited | Administrative & support | 2025 |
| Matt Gaskell Limited | Administrative & support | 2020 |
| Maxika Homes (Henley) Ltd | Real estate | 2024 |
| Maximum AV Ltd | Administrative & support | 2011 |
| Maxwell Place Management Limited | Households | 2003 |
| Mazlum Ltd | Other services | 2017 |
| MBK Marketing Ltd | Administrative & support | 2003 |
| Mbri Ltd | Professional & scientific | 2026 |
| Mclaren and Partners Limited | Administrative & support | 2006 |
| MD Dovercourt Limited | Real estate | 2021 |
| Meadows Farm Studios Limited | Professional & scientific | 1998 |
| Measurably Better Limited | Professional & scientific | 2024 |
| Medco Energi Thailand (E&P) Limited | Mining & quarrying | 2005 |
| Mediamingle Limited | Administrative & support | 2025 |
| Meglio Limited | Wholesale & retail | 2016 |
| Memorable Experiences Ltd | Administrative & support | 2025 |
| Mercers Law LLP | | 2022 |
| Meridian Family Investments Company Limited | Professional & scientific | 2025 |
| Mermaid Yard Clearance Limited | Water & waste | 2019 |
| Messe Transport Limited | Wholesale & retail | 2025 |
| Metcalfe Lawn Care Limited | Households | 2022 |
| Metiderma Ltd | Health & social care | 2023 |
| Metis Consultancy Intl. Ltd. | Professional & scientific | 2016 |
| Metro Student Accommodation Limited | Real estate | 2013 |
| Mettryx Ltd | Professional & scientific | 2021 |
| MF Racing Limited | Professional & scientific | 2017 |
| Mg&A Ltd | Professional & scientific | 2014 |
| MGK Holdings Ltd | Wholesale & retail | 2020 |
| MI40 Ltd | Information & communication | 2023 |
| Michiko London Ltd | Professional & scientific | 2012 |
| Micro Consultancy Services Ltd | Information & communication | 2026 |
| Mid-Century Living Ltd | Extraterritorial | 2021 |
| Midiamant Investment Limited | Real estate | 2015 |
| Midmar Nominee Holdings Limited | Extraterritorial | 2021 |
| Mike Barry Eco Ltd | Professional & scientific | 2019 |
| Mikrofill 2000 Limited | Professional & scientific | 2000 |
| Mikrofill Systems Limited | Manufacturing | 1995 |
| Milkstix Limited | Extraterritorial | 2004 |
| Mill END Management Company Limited | Real estate | 1998 |
| Mill END Property Holdings Ltd | Real estate | 2023 |
| Mill END Property Management Ltd | Real estate | 2023 |
| Million Cars Limited | Transport & logistics | 2016 |
| Millionaire Next Door Limited | Professional & scientific | 2012 |
| Mimir Labs Ltd | Information & communication | 2023 |
| Minariel Tutors Ltd | Education | 2025 |
| Mini-Tankers Ltd | Transport & logistics | 2012 |
| Ministone Limited | Wholesale & retail | 1995 |
| Minus Limited | Professional & scientific | 2015 |
| Miroo Early Years Ltd | Education | 2025 |
| Miss Cufflinks Ltd | Wholesale & retail | 2007 |
| MIT Environmental Monitoring Limited | Extraterritorial | 2004 |
| Mjlj Investments LLP | | 2026 |
| Mkmc International Ltd | Professional & scientific | 2020 |
| MM Electrical Contractors Henley Limited | Construction | 2023 |
| MMD Physio Limited | Other services | 2021 |
| MO Gannon & Associates Ltd | Professional & scientific | 2011 |
| Moatevate Consultancy Ltd | Professional & scientific | 2026 |
| Mode Recruitment Ltd | Administrative & support | 2017 |
| Moffett Consulting Limited | Professional & scientific | 2024 |
| Moli Consulting Limited | Professional & scientific | 2024 |
| Monarch's BOW (Wantage) Management Company Limited | Households | 2017 |
| Montaggio UK Limited | Information & communication | 2026 |
| Montrose Clinic Ltd | Other services | 2021 |
| Montrose London Ltd | Professional & scientific | 2021 |
| Montrose London Medical Limited | Health & social care | 2025 |
| Montrose Residential Limited | Hospitality | 2008 |
| Moonscape Media Limited | Information & communication | 2002 |
| Morden Wolf Ltd | Information & communication | 2020 |
| More IT Accounting Ltd | Professional & scientific | 2017 |
| Morgan Lockyer Limited | Professional & scientific | 2002 |
| Morgans Electrical Services Ltd | Construction | 2007 |
| Morton & Comonte Limited | Professional & scientific | 2013 |
| Mother of ALL Jewels Ltd | Manufacturing | 2025 |
| Mother Sister Daughter CIC | Hospitality | 2022 |
| Motolec Properties Limited | Construction | 2017 |
| Mountainmutton Content & Creative Ltd | Professional & scientific | 2018 |
| Move Ventures Ltd | Financial services | 2017 |
| Move Well Limited | Arts & recreation | 2026 |
| Moving Image Works Ltd | Professional & scientific | 2010 |
| Mpbp Group Limited | Manufacturing | 2019 |
| MPH Communications Limited | Professional & scientific | 2002 |
| MR Blad's Barber Ltd | Other services | 2026 |