| Manbrella Limited | Manufacturing | 2018 |
| Mandmdogwash Limited | Other services | 2025 |
| Manea GA Transport Ltd | Transport & logistics | 2024 |
| Maneboard Limited | Professional & scientific | 1990 |
| Mann Value Ltd | Wholesale & retail | 2023 |
| Mannicitas Limited | Hospitality | 2017 |
| Manor Court (Herriard) Limited | Households | 2005 |
| Manor Farm Residents Company Limited | Households | 2017 |
| Manpower Supply Ltd | Professional & scientific | 2019 |
| Mansion DE VIL Ltd | Information & communication | 2026 |
| Manuswa Limited | Information & communication | 2019 |
| Manx Collections Limited | Administrative & support | 1991 |
| Many Hats Brew Club Limited | Manufacturing | 2019 |
| Manydown Garden Communities LLP | | 2018 |
| MAO LIN Ltd | Other services | 2025 |
| Maple & T Ventures Ltd | Real estate | 2024 |
| Maraya Ltd | Transport & logistics | 2014 |
| Marbo Global Healthcare Ltd | Professional & scientific | 2021 |
| Marbo Global Investments Ltd | Administrative & support | 2011 |
| Marcap Investments Limited | Real estate | 2025 |
| March Merck Limited | Manufacturing | 2020 |
| Marchant Building Services Ltd | Construction | 2010 |
| Marcin Home Improvements Ltd | Construction | 2022 |
| Marexim Ltd | Wholesale & retail | 2023 |
| Margaret Norris Designs Limited | Health & social care | 2015 |
| Marie Davis Court Management Company Limited | Households | 1985 |
| Marigold Blossom Limited | Real estate | 2022 |
| Marina Solutions International Limited | Administrative & support | 2017 |
| Marine Blueprints Consulting Ltd | Professional & scientific | 2024 |
| Marine Heating Limited | Construction | 2016 |
| Marinus Fuel Limited | Wholesale & retail | 2022 |
| Marinus Properties Ltd | Real estate | 2020 |
| Mario Motors Ltd | Wholesale & retail | 2025 |
| Maritime Digital Hub Limited | Administrative & support | 2020 |
| Maritime Orient and Neareast Agency Limited | Financial services | 1954 |
| Marius Barbu Trans Ltd | Transport & logistics | 2019 |
| Mark Corder Ltd | Professional & scientific | 2015 |
| Mark Glenn Ltd | Health & social care | 2001 |
| Mark Trodd MVS Ltd | Wholesale & retail | 2016 |
| Mark Upton Project Support Ltd | Administrative & support | 2010 |
| Marketing for Entrepreneurs Limited | Professional & scientific | 2016 |
| Marketing Traction International Limited | Professional & scientific | 2007 |
| Marketmate Solutions Ltd | Wholesale & retail | 2025 |
| Markiancarter Consulting Ltd | Information & communication | 2022 |
| Marli PUB Company Limited | Hospitality | 2015 |
| Marlyn Electrical Ltd | Construction | 2013 |
| Marnel Consulting Limited | Professional & scientific | 2023 |
| Marni Properties Limited | Real estate | 2020 |
| Marquez Engineering Group Ltd | Professional & scientific | 2025 |
| Marsay SMC Limited | Information & communication | 2014 |
| Marsek Ltd | Transport & logistics | 2019 |
| Marshè Service Ltd. | Administrative & support | 2016 |
| Martello Creative Ltd | Administrative & support | 2015 |
| Martin Cole Plumbing Limited | Construction | 2005 |
| Martin K Limited | Wholesale & retail | 2019 |
| Martin Keyte Financial Planning Limited | Financial services | 2006 |
| Martin Lipovyanov Limited | Health & social care | 2013 |
| Martin Matthewson Holdings Limited | Manufacturing | 2019 |
| Martin Matthewson Limited | Manufacturing | 2000 |
| Martin R Coleman (Osteopath) Ltd | Health & social care | 2002 |
| Martin's Bookkeeping and Accountancy Services Limited | Administrative & support | 2002 |
| Martins Selfdrive Service Limited | Administrative & support | 1993 |
| Martor UK Limited | Wholesale & retail | 1995 |
| Martp Ltd | Wholesale & retail | 2024 |
| Marty Tours Limited | Administrative & support | 2018 |
| Maryam's Tech Ltd | Wholesale & retail | 2025 |
| Maryna Jenkins Limited | Education | 2023 |
| Master KA Consulting Limited | Professional & scientific | 2014 |
| Master Plaster Works Limited | Construction | 2025 |
| Mastercontrol Global Limited | Information & communication | 1995 |
| Mastervale Limited | Extraterritorial | 1993 |
| Mastic Sealant Solutions Ltd | Construction | 2017 |
| Matchlock Games Ltd | Wholesale & retail | 2015 |
| Material Supplies Group Ltd | Wholesale & retail | 2019 |
| Material Supplies Ltd | Wholesale & retail | 2019 |
| Mathias Auto Locksmith Ltd | Other services | 2026 |
| Matley Design Ltd | Professional & scientific | 2011 |
| Matt Hall Consulting Ltd | Information & communication | 2022 |
| Matteo Rossillo Consulting Ltd | Manufacturing | 2024 |
| Matthew J Smith Construction Ltd | Construction | 2018 |
| Matthew Ryan Construction Limited | Construction | 2014 |
| Matthews Roofing Services Ltd | Construction | 2025 |
| Maverick Media Services Limited | Information & communication | 2024 |
| Maverick Talent Limited | Administrative & support | 2012 |
| Maxma Care Services Ltd | Health & social care | 2022 |
| Maxpdf Editor Ltd | Information & communication | 2025 |
| MAY Bedrock Property Group Ltd | Construction | 2025 |
| Maya Decorations Limited | Hospitality | 2026 |
| Mayaz Beautybiz Ltd | Other services | 2023 |
| Maycare Limited | Health & social care | 2009 |
| Mayflower Chinese Food Ltd | Hospitality | 2022 |
| Mayflower Foods Ltd | Hospitality | 2026 |
| Mayfly Insight Limited | Professional & scientific | 2021 |
| Mayk Motorcycle Ltd | Wholesale & retail | 2022 |
| Mayor (UK) Limited | Extraterritorial | 1991 |
| Mazo MK Ltd | Transport & logistics | 2020 |
| MB Roofing Solutions Ltd | Construction | 2016 |
| MBE Thermal Spray Services Ltd | Professional & scientific | 2020 |
| Mbfb Limited | Professional & scientific | 2015 |
| MBK Ltd | Administrative & support | 2013 |