| Mango Marquees Ltd | Administrative & support | 2021 |
| Manhatan Ltd | Construction | 2016 |
| Manibra Ltd | Wholesale & retail | 2026 |
| Manikonda Technologies Limited | Information & communication | 2016 |
| Manor Court Kitchens Ltd | Manufacturing | 2019 |
| Manor Mount (Freehold) Limited | Households | 2007 |
| Manor River Freight Services Limited | Transport & logistics | 2003 |
| Manor Road Limited | Real estate | 2018 |
| Mansfield Solicitors & Advocates Limited | Professional & scientific | 2011 |
| Maol Holdings Ltd | Information & communication | 2023 |
| MAP Specification UK Ltd | Construction | 2025 |
| Maple Court (Croydon) Management Company Limited | Households | 1976 |
| Maple House Bromley Limited | Hospitality | 2024 |
| Maple Oak Limited | Administrative & support | 2025 |
| Maple Park Limited | Administrative & support | 2025 |
| Maple Rail Consultancy Ltd | Transport & logistics | 2025 |
| Maplerose Limited | Information & communication | 2024 |
| Maraida Limited | Extraterritorial | 2004 |
| Marazion Estates Limited | Construction | 1997 |
| Marble Hair and Beauty Limited | Other services | 2019 |
| Marble Restore Limited | Construction | 2016 |
| Marble Services Limited | Construction | 2003 |
| Marcel Computing Ltd | Information & communication | 2013 |
| Mardle Developments Limited | Construction | 2007 |
| Mari Kitchen Ltd | Hospitality | 2025 |
| Maria Cochrane Limited | Wholesale & retail | 2015 |
| Marian Cake Studio Limited | Manufacturing | 2022 |
| Marie-Claire Limited | Health & social care | 2015 |
| Mario's Cleaning & Removal Ltd | Transport & logistics | 2025 |
| Mariscal-Faulds CMC Ltd. | Professional & scientific | 2016 |
| Mark Attree Ltd | Professional & scientific | 2015 |
| Mark Design and Development Limited | Real estate | 1985 |
| Mark Fitzgerald Limited | Manufacturing | 2014 |
| Mark II Property Investments Limited | Real estate | 2016 |
| Mark Perry Limited | Administrative & support | 2005 |
| Mark Tiffany Communications Limited | Administrative & support | 2013 |
| Marketing Logic Ltd | Information & communication | 2025 |
| Marketing Partnerships Ltd | Information & communication | 2012 |
| Marley Building Consultancy Ltd | Professional & scientific | 2022 |
| Marley Properties UK Ltd | Real estate | 2021 |
| Marlix Brewing Company Limited | Manufacturing | 2020 |
| Marmo Limited | Construction | 2020 |
| Martin Casting Limited | Arts & recreation | 2025 |
| Martin Court Limited | Households | 2000 |
| Martin Family Assets Ltd | Financial services | 2026 |
| Martin Gayford and Company Limited | Manufacturing | 2022 |
| Martins Delivery Services Ltd | Transport & logistics | 2017 |
| Martinvest Limited | Real estate | 2024 |
| Mary ANN Horgan Properties Ltd | Real estate | 2019 |
| Mary Rose Hotel Limited | Hospitality | 2006 |
| Maryfab Limited | Wholesale & retail | 2026 |
| MAS Accountancy Limited | Professional & scientific | 2020 |
| MAS GRP Ltd | Professional & scientific | 2025 |
| Masala Dabbas Foods Ltd | Hospitality | 2017 |
| Masma Property Ltd | Real estate | 2022 |
| Masma Solutions Limited | Information & communication | 2014 |
| Mason Lewis Consultants Limited | Information & communication | 2021 |
| Mason Solutions Ltd | Construction | 2017 |
| Masons Hill Stamp Shop Limited | Wholesale & retail | 2017 |
| Masquerade Events Ltd | Professional & scientific | 2016 |
| Mastana Positive Ltd | Transport & logistics | 2019 |
| Master Build Carpentry Ltd | Construction | 2021 |
| Master Esfihas Ltd | Manufacturing | 2024 |
| Master Planner Limited | Real estate | 2020 |
| MAT Chaplin Limited | Arts & recreation | 2014 |
| Match Worldwide Investments Ltd | Real estate | 2013 |
| Matchedfx Private Limited | Information & communication | 2021 |
| Matera City Pass Ltd | Information & communication | 2025 |
| Matka Group Limited | Professional & scientific | 2025 |
| Matt Gant Construction Ltd | Information & communication | 2016 |
| Matt Shurmer Driving School Ltd | Education | 2014 |
| Mattcom Ltd | Information & communication | 2025 |
| Matthew Adams Limited | Wholesale & retail | 2011 |
| Mattstella Property Limited | Real estate | 2026 |
| Maven Marketing Ltd | Professional & scientific | 2023 |
| Mavovo Ltd | Health & social care | 2019 |
| MAX Blake Ltd | Information & communication | 2019 |
| MAX Change Consulting Ltd | Professional & scientific | 2024 |
| MAX Drive Limited | Wholesale & retail | 2014 |
| MAX26 Investments Limited | Arts & recreation | 2024 |
| Maxident Property Limited | Real estate | 2015 |
| Maxim Apartments (Bromley) RTM Company Limited | Real estate | 2015 |
| Maxrite Ltd | Professional & scientific | 2016 |
| MAY Living Ltd | Health & social care | 2026 |
| Maya Fragrances Limited | Wholesale & retail | 2022 |
| MAYA101PVT Limited | Real estate | 2023 |
| Mayaza Limited | Professional & scientific | 2021 |
| Maynard Nelson Limited | Real estate | 2022 |
| Mayron Ltd | Construction | 2013 |
| Mays Housing Ltd | Extraterritorial | 2025 |
| MAZ Exchange Group Limited | Professional & scientific | 2020 |
| Maze Solutions Limited | Information & communication | 2010 |
| MB Coaching and Teaching Service UK Ltd | Education | 2022 |
| MB Groundwork & Design Limited | Professional & scientific | 2025 |
| MB Property Sales Limited | Real estate | 2023 |
| MBH Ltd | Construction | 2008 |
| MBR Consultancy Ltd | Information & communication | 2013 |
| MC Brewery Ltd | Hospitality | 2024 |
| Mcevoy B&M Limited | Construction | 2021 |
| MCJ Security Ltd. | Administrative & support | 2018 |