| Meljardes Ltd | Real estate | 2024 |
| Mellow Online Limited | Wholesale & retail | 2025 |
| Melville Marketing Solutions Limited | Professional & scientific | 2016 |
| Memory Eyecare Limited | Professional & scientific | 2024 |
| Menacon Ltd | Information & communication | 2026 |
| Mendip Chase Management Company Limited | Households | 2008 |
| Merakies Events Limited | Other services | 2019 |
| Mercy Drops Ltd | Health & social care | 2025 |
| Mere Lane Management Company Limited | Households | 2006 |
| Meridian (Bristol) Management Company Limited | Households | 2008 |
| Meridian Hub Ltd | Information & communication | 2026 |
| Meridian Property Development Ltd | Construction | 2019 |
| Meridian Surveys Limited | Professional & scientific | 2014 |
| Meriye Concepts Ltd | Hospitality | 2025 |
| Merlet Limited | Extraterritorial | 2009 |
| Merlin Lighting (Installations) Limited | Construction | 2006 |
| Merlin Rise (Facilities Management) Limited | Households | 2020 |
| Merlo Veterinary Imaging Ltd | Professional & scientific | 2006 |
| Merlott Ltd | Professional & scientific | 2020 |
| Merryleas Holdings Ltd | Financial services | 2025 |
| Merwen Dartash Ltd | Real estate | 2021 |
| Meshii Group Limited | Information & communication | 2022 |
| Metaldealers Ltd. | Extraterritorial | 1999 |
| Metaltec Holding Limited | Financial services | 2022 |
| Metaltec Limited | Manufacturing | 2001 |
| Metcalfe Business Solutions Ltd | Professional & scientific | 2016 |
| Metis Cognition Limited | Health & social care | 2011 |
| Metis Support Ltd | Professional & scientific | 2017 |
| Metivy Limited | Hospitality | 2020 |
| Metre Candles Ltd | Wholesale & retail | 2024 |
| Metri Measurements Limited | Extraterritorial | 2015 |
| Metroworth Consulting (Europe) Limited | Administrative & support | 2005 |
| MFR Developments Ltd | Real estate | 2025 |
| MG Asset Holding UK Limited | Real estate | 2024 |
| MGT Construction (Southern) Ltd | Construction | 2007 |
| MH - Fire and Security Services Ltd | Construction | 2025 |
| MH Aesthetics Ltd | Health & social care | 2017 |
| MH Holding Limited | Administrative & support | 2023 |
| MH Property Consultants Limited | Professional & scientific | 2018 |
| MHT Corporate Limited | Hospitality | 2023 |
| MHT Electrical Limited | Construction | 2019 |
| MIB Rail Limited | Professional & scientific | 2013 |
| Miba Food&Drink Solution Ltd | Hospitality | 2019 |
| Michael Cadier Aesthetic Surgery Limited | Health & social care | 2009 |
| Michael Lyons Architecture Limited | Professional & scientific | 1999 |
| Michael Paterson & Associates Limited | Administrative & support | 1999 |
| Michael Rath Brass Musical Instruments Limited | Manufacturing | 2001 |
| Michael Ward Limited | Manufacturing | 1985 |
| Michelle Haste Limited | Professional & scientific | 2012 |
| Midas 2000 Ltd | Arts & recreation | 2000 |
| Middleton-Croft Ltd | Administrative & support | 2024 |
| Midforest Building Ltd | Construction | 2013 |
| Midhurst Child Care Limited | Health & social care | 2005 |
| Midhurst Clinical Therapeutic Services Limited | Professional & scientific | 2020 |
| Midhurst Holdings Limited | Administrative & support | 2007 |
| Midhurst Learning Limited | Education | 2021 |
| Midrange Direct Limited | Information & communication | 1999 |
| Midsomer Homecare Limited | Health & social care | 2026 |
| Mies (UK) Ltd | Professional & scientific | 2012 |
| Mighty Oak Joinery Ltd | Construction | 2024 |
| Migrate Data Limited | Information & communication | 1996 |
| Mike Badger Ltd | Professional & scientific | 2015 |
| Mike Stokes Ltd | Wholesale & retail | 2019 |
| Milan GW Limited | Construction | 2011 |
| Milards Ltd | Real estate | 2017 |
| Milcase Ltd | Wholesale & retail | 2019 |
| Military Engineering Experimental Establishment | Professional & scientific | 2021 |
| Miliwheel Ltd | Information & communication | 2026 |
| Millar Media Ltd | Information & communication | 2023 |
| Millchurch Farms Ltd | Agriculture & fishing | 2025 |
| Millchurch Holdings Ltd | Financial services | 2025 |
| Millchurch Ltd | Agriculture & fishing | 2025 |
| Millennium Construction & Maintenance (Southern) Limited | Extraterritorial | 2006 |
| Millennium Construction & Maintenance UK Limited | Construction | 1999 |
| Miller Properties Ltd | Households | 2022 |
| Miller, Turner & Co., (U.K.) Limited | Administrative & support | 1982 |
| Millers Wood Management Company Limited | Real estate | 2019 |
| Millersmind Ltd | Manufacturing | 2024 |
| Millfield House Residents Management Company Limited | Households | 2025 |
| Millfields Middleton Company Limited | Households | 2020 |
| Milliemint Limited | Wholesale & retail | 2024 |
| Milligan Facilities & Asset Management Limited | Real estate | 2025 |
| Millpond Advisory Ltd | Professional & scientific | 2026 |
| Mills Beech Limited | Agriculture & fishing | 2010 |
| Mills Way Management Company Limited | Real estate | 2002 |
| Milston Flower Barn Ltd | Wholesale & retail | 2019 |
| Milton Abbey Heritage Trust | Other services | 2015 |
| Mimir Human Factors Ltd | Professional & scientific | 2022 |
| Mindarie Holdings Limited | Real estate | 2025 |
| Minden Enterprises Ltd | Real estate | 2017 |
| Minden Hills Ltd | Real estate | 2023 |
| Mindlight Consulting Limited | Administrative & support | 2013 |
| Mindlight Investments Limited | Real estate | 2019 |
| Mindstorm Coding Ltd | Education | 2023 |
| Mine (Shaftesbury) Limited | Wholesale & retail | 2017 |
| Mineral Engineering Processes Limited | Manufacturing | 1985 |
| Ming's Garden (Salisbury) Ltd | Hospitality | 2021 |
| Mini Professors Global Limited | Education | 2014 |
| Mini Professors Limited | Education | 2012 |
| Minifest Limited | Construction | 2018 |