| Maple Grove Management Company Limited | Real estate | 2011 |
| Maple Place Estates Ltd | Households | 2018 |
| Mapmycar Group Limited | Wholesale & retail | 2013 |
| Maps POL Ltd | Wholesale & retail | 2017 |
| MAQ ALI Holdings Ltd | Real estate | 2026 |
| MAR Accountants & Tax Consultants Ltd | Professional & scientific | 2021 |
| MAR E-Commerce Ltd | Extraterritorial | 2020 |
| Mara Rail Ltd | Construction | 2016 |
| Maraal Systems Ltd | Wholesale & retail | 2024 |
| Marabese Ceramics Holdings Limited | Financial services | 2022 |
| Marabese Interiors Limited | Wholesale & retail | 2025 |
| Marathon for Mental Health Ltd | Health & social care | 2025 |
| Marba Properties Ltd | Extraterritorial | 2019 |
| Marble Springs Limited | Hospitality | 2024 |
| Marble Tiling South Ltd | Construction | 2025 |
| Marc Property Improvement Limited | Construction | 2019 |
| Marcaulay Group Ltd | Information & communication | 2022 |
| Marcello Pizzeria Trattoria Ltd | Hospitality | 2015 |
| March Accountants Ltd | Professional & scientific | 2021 |
| Marchan Holdings Limited | Financial services | 2023 |
| Marchiss Limited | Professional & scientific | 2022 |
| Marcin Nowak Service Ltd | Wholesale & retail | 2018 |
| Marcin Pelikan Body Shop Ltd | Other services | 2015 |
| Marcin Sandomierski Limited | Wholesale & retail | 2016 |
| Marcin Toczek Limited | Wholesale & retail | 2016 |
| Marco L Colombo Box Limited | Wholesale & retail | 2025 |
| Marco L Colombo Limited | Wholesale & retail | 2025 |
| Marco's Property Services Ltd | Construction | 2018 |
| Marcon Property Management Ltd | Real estate | 2019 |
| Marcu Motors Ltd | Wholesale & retail | 2025 |
| Marcus Hill Limited | Information & communication | 2022 |
| Marcus Hill Other Limited | Wholesale & retail | 2023 |
| Marcus Read Security Ltd | Administrative & support | 2023 |
| Margeritta Limited | Wholesale & retail | 2017 |
| Margo's Woburn Limited | Hospitality | 2024 |
| Mari Logistics Ltd | Construction | 2018 |
| Maria & Khad Ltd | Health & social care | 2022 |
| Maria Grazia Salon Limited | Other services | 2016 |
| Maria Jewell Ltd | Health & social care | 2014 |
| Maria Theresa Research Innovation and Development Ltd | Education | 2024 |
| Marian Builders Limited | Real estate | 1964 |
| Marian Haulage Limited | Wholesale & retail | 2024 |
| Mariantex Forwarding PC | | 2017 |
| Marie’S Cleaning Services Ltd | Administrative & support | 2019 |
| Marie’S Properties Limited | Hospitality | 2019 |
| Marika Ltd | Transport & logistics | 2011 |
| Marina Engineering Limited | Real estate | 2009 |
| Marine Cargo Experts Limited | Professional & scientific | 2004 |
| Marion Hirst Ltd | Professional & scientific | 2016 |
| Marius Construction Ltd | Construction | 2026 |
| Marius Vandra Ltd | Wholesale & retail | 2023 |
| Mark and Rose Limited | Financial services | 2011 |
| Mark Draper Ltd | Health & social care | 2013 |
| Mark Early Build Limited | Construction | 2018 |
| Mark FIX Ltd | Wholesale & retail | 2014 |
| Mark Flashman Ltd. | Professional & scientific | 2014 |
| Mark Rutherford School Trust | Education | 2012 |
| Mark Slaughter Ltd | Other services | 2017 |
| Mark Smith Trade Vehicles Ltd | Wholesale & retail | 2021 |
| Mark the Designer Ltd | Professional & scientific | 2025 |
| Mark Todhunter Ltd | Administrative & support | 2002 |
| Mark's Automotive Engineering Ltd. | Wholesale & retail | 2015 |
| Markham Motors Ltd | Manufacturing | 2021 |
| Markham Ventures Limited | Financial services | 2024 |
| Markhoar Limited | Other services | 2025 |
| Marko 27 Ltd | Transport & logistics | 2024 |
| Marko Direct Ltd | Transport & logistics | 2017 |
| Marks & Punctures Tattoos & Piercings Ltd | Other services | 2019 |
| Marks Group Ltd | Real estate | 2015 |
| Marks Holdings Limited | Extraterritorial | 2008 |
| Marks Trust | Other services | 2012 |
| Marks Ventures Ltd | Extraterritorial | 2015 |
| Markworld Limited | Real estate | 2017 |
| Marlex Projects Ltd | Professional & scientific | 2025 |
| Marley Consultancy Services Limited | Real estate | 2008 |
| Marley Support Consultants Ltd | Administrative & support | 2023 |
| Marlynton & Partners Holdings Limited | Wholesale & retail | 2005 |
| Marmy Limited | Health & social care | 2014 |
| Marok Foods UK Limited | Wholesale & retail | 2025 |
| Maroo Ltd | Real estate | 2018 |
| Marpe Limited | Health & social care | 2025 |
| Marquee World Limited | Administrative & support | 2020 |
| Marquees With Pryde Limited | Other services | 2010 |
| Marrequinha Limited | Professional & scientific | 1988 |
| Mars-Jones Limited | Transport & logistics | 1950 |
| Marsh Farm Biogas Limited | Energy | 2013 |
| Marsh Leys Limited | Agriculture & fishing | 1964 |
| Marsh Residential Surveyors Ltd | Real estate | 2025 |
| Marshall Waller Ltd | Construction | 2012 |
| Marston Flooring Ltd | Construction | 2020 |
| Marston Moretaine Engineering Ltd | Manufacturing | 2022 |
| Marston Pomona Landscaping Solutions Limited | Administrative & support | 2023 |
| Marston Vale Farms Limited | Agriculture & fishing | 2008 |
| Marston Vale Services Trading AS the Forest Centre Limited | Agriculture & fishing | 1998 |
| Marston Vale Tree Care Ltd | Agriculture & fishing | 2018 |
| Martell Drive Management Limited | Households | 2025 |
| Martfor Express Ltd | Transport & logistics | 2025 |
| Martiemart Ltd | Wholesale & retail | 2026 |
| Martin & Karl Ltd | Construction | 2025 |
| Martin Burgess Logistics Ltd | Transport & logistics | 2009 |