| Mijag Property Services Limited | Real estate | 2017 |
| Mike Tippins Design Limited | Professional & scientific | 2002 |
| Miketara Properties Ltd | Real estate | 2020 |
| Mill Court Medical Services Limited | Health & social care | 2012 |
| Mill Floorings (Notts) Ltd | Wholesale & retail | 2013 |
| Mill House Properties (Wales) Ltd | Real estate | 2000 |
| Mill Park Road Management Services Ltd | Real estate | 2021 |
| Millennium (Bearings and Transmissions) Ltd | Wholesale & retail | 1996 |
| Milner Properties Ltd | Real estate | 2016 |
| Milsy Limited | Other services | 2026 |
| Milu Group Limited | Financial services | 2023 |
| Milu Property Investments Ltd | Real estate | 2022 |
| Mind Thai Ltd | Hospitality | 2022 |
| Mingardi Magnetic (UK) Limited | Extraterritorial | 2002 |
| Mini ME Yoga Ltd | Education | 2021 |
| Ministry of Kindness Ltd | Education | 2022 |
| Minster Computer Systems Limited | Information & communication | 1988 |
| Minster Court RTM Company Limited | Households | 2018 |
| Minster Mews Management Company 2025 Limited | Households | 2025 |
| Minsterley Investments Ltd | Real estate | 2022 |
| Mitchel LEE Risk Solutions LLP | | 2024 |
| Mitchell and SON Motors Limited | Wholesale & retail | 2025 |
| Miworld Business Services Limited | Administrative & support | 2018 |
| Miworld Legal Services Limited | Financial services | 2020 |
| Miworld Services Limited | Administrative & support | 2017 |
| Miworld Wealth Management Limited | Professional & scientific | 2019 |
| MJ Fresh Lemon Ltd | Administrative & support | 2025 |
| MJ Motors (Burntwood) Ltd | Wholesale & retail | 2011 |
| MJF Plant Training Limited | Education | 2021 |
| MJK Pharma Limited | Professional & scientific | 2022 |
| MJM Consultancy Services Limited | Professional & scientific | 2015 |
| MJR Coats Ltd | Real estate | 2021 |
| MJS Leadership Ltd | Professional & scientific | 2019 |
| MKN Electrical Limited | Construction | 2007 |
| MLJ Installs Ltd | Construction | 2025 |
| MLR Group Limited | Financial services | 2025 |
| MLR Independent Porsche Specialists Ltd | Wholesale & retail | 2020 |
| MNC Group Ltd | Professional & scientific | 2025 |
| Mobac Services Limited | Construction | 2005 |
| MOD Shoes Limited | Wholesale & retail | 2013 |
| Moda Milano Bags Ltd | Wholesale & retail | 2025 |
| Mode Laser Skin Clinic Limited | Health & social care | 2008 |
| Modern Move Group Limited | Other services | 2024 |
| Modern Painting Contractors Limited | Construction | 2001 |
| Mohammeds Indian Village Ltd | Hospitality | 2018 |
| Mohava Limited | Information & communication | 2016 |
| Mojo Vehicle Sales Ltd | Wholesale & retail | 2020 |
| Molbarn Limited | Hospitality | 2023 |
| Mon-Maison Ltd | Wholesale & retail | 2018 |
| Monarch - ELS Properties Limited | Real estate | 2013 |
| Monarch-Els Limited | Transport & logistics | 2008 |
| Monek Data Services Limited | Information & communication | 2017 |
| Monek Group Limited | Information & communication | 2017 |
| Monek Limited | Information & communication | 2015 |
| Monek Merchant Services Ltd | Information & communication | 2019 |
| Monetium Private Wealth Management Ltd | Professional & scientific | 2011 |
| Money Making Expert Limited | Extraterritorial | 2018 |
| Monica Inc Ltd | Transport & logistics | 2016 |
| Monitec Limited | Financial services | 2016 |
| Monkeypants Productions Limited | Information & communication | 2010 |
| Monozygotic Limited | Professional & scientific | 2026 |
| Moonraker Charters Ltd | Transport & logistics | 2022 |
| Moonrocket Promotions Limited | Arts & recreation | 2025 |
| Moores Agri Limited | Extraterritorial | 2026 |
| Moores Orthopaedics Ltd | Health & social care | 2021 |
| Morceran Ltd | Transport & logistics | 2019 |
| More Thought for Food Limited | Wholesale & retail | 2006 |
| MORESPACE4U Garden Buildings Ltd | Administrative & support | 2019 |
| Morgan Lang Limited | Administrative & support | 2001 |
| Morgan Textile Agencies Limited | Professional & scientific | 1990 |
| Morleys Investment Company Limited | Real estate | 2020 |
| Morrey Care Group Limited | Financial services | 2024 |
| Morrey Care Limited | Other services | 2019 |
| Mosaic Branding Ltd | Professional & scientific | 2026 |
| Most Wanted Bistro Limited | Hospitality | 2021 |
| Mother BEE Limited | Manufacturing | 2026 |
| Motif Imagery Ltd | Professional & scientific | 2025 |
| Motif Investments Ltd | Financial services | 2026 |
| Motivation Hub Ltd | Health & social care | 2025 |
| Motivetime Limited | Information & communication | 1988 |
| Motorczar Consulting Ltd | Professional & scientific | 2016 |
| Mountpaz Holdings Ltd | Financial services | 2022 |
| Move & Connect C.I.C. | Arts & recreation | 2025 |
| MOVE2DIGITAL Ltd | Information & communication | 2025 |
| Mowgli Events Ltd | Administrative & support | 2019 |
| Moxiemomentum Limited | Information & communication | 2018 |
| Moyavox Voice Solutions Ltd | Information & communication | 2012 |
| Mpess Limited | Professional & scientific | 2012 |
| MPO 796 Ltd | Real estate | 2021 |
| MPR Professional Caddie Services Ltd | Arts & recreation | 2025 |
| MPS Squared Limited | Administrative & support | 2024 |
| Mpwr Group Ltd | Education | 2024 |
| Mpwr Group UK CIC | Education | 2025 |
| MR Move Ltd | Transport & logistics | 2024 |
| MR Simms Caledonia Ltd | Wholesale & retail | 2012 |
| MR Tyre (Motor Sport) Limited | Wholesale & retail | 2002 |
| MR. Tyre Limited | Wholesale & retail | 1991 |
| MRE Professional Engineering Services Limited | Professional & scientific | 2015 |
| MRK Utilities Ltd | Energy | 2026 |
| Mrrj Birmingham Ltd | Real estate | 2024 |