| Melsie Holder Ltd | Health & social care | 2011 |
| Meltworx Limited | Information & communication | 2022 |
| Melville Investment and Consulting Ltd | Real estate | 2020 |
| Mena LUX Ltd | Wholesale & retail | 2023 |
| Menace Holdings Ltd | Financial services | 2023 |
| Mence Media Ltd | Information & communication | 2025 |
| Mencel Transport Ltd | Transport & logistics | 2015 |
| Mendit Windows & Doors Limited | Extraterritorial | 2015 |
| Mental Health Views Limited | Health & social care | 2017 |
| Mentality Manual Limited | Extraterritorial | 2023 |
| Mentoring Limited | Health & social care | 2025 |
| Meraki Creative Limited | Professional & scientific | 2017 |
| Meraki Technology Limited | Information & communication | 2024 |
| Meraviglio Ltd | Administrative & support | 2026 |
| Merax Financial Ltd | Information & communication | 2017 |
| Mercian Consulting (Engineers) Limited | Professional & scientific | 2026 |
| Mercified Products Limited | Wholesale & retail | 2026 |
| Mercora Ltd | Wholesale & retail | 2025 |
| Meridian Air Conditioning Limited | Energy | 2013 |
| Meridian Building Services Limited | Construction | 2025 |
| Meridian Carpentry & Build Limited | Extraterritorial | 2016 |
| Meridian Data Limited | Construction | 2026 |
| Meridian Electrical Contracting Limited | Construction | 2005 |
| Meridian Electrical Holdings Limited | Construction | 2019 |
| Meridian Group South Ltd | Manufacturing | 2019 |
| Meridian Heat Pumps Limited | Construction | 2019 |
| Meridian Hvac Limited | Extraterritorial | 2016 |
| Meridian Lifts Limited | Construction | 2002 |
| Meridian Rachp Training Limited | Extraterritorial | 2022 |
| Meridian Refrigeration Limited | Energy | 2015 |
| Meridian Ventilation Limited | Construction | 2019 |
| Meridian Ventilation Systems Limited | Construction | 2003 |
| Meridius Consulting Limited | Administrative & support | 2016 |
| Meridius Labs Ltd | Information & communication | 2025 |
| Merill Games Ltd | Information & communication | 2024 |
| Merley Properties Limited | Real estate | 2005 |
| Merlin (2020) Limited | Construction | 2018 |
| Merlin the Cat Ltd | Real estate | 2024 |
| Merryfield Business Management Services Limited | Construction | 1978 |
| Merton Court (Parkstone) Limited | Other services | 1960 |
| Mesh AI Limited | Information & communication | 2021 |
| Mesh Consulting Limited | Professional & scientific | 2024 |
| Mesonomics Ltd | Information & communication | 2019 |
| Mess Events Ltd | Other services | 2022 |
| Messrs. Birles & Company, Shipwrights, (UK), Limited | Manufacturing | 2024 |
| Meta Capital Dorset Ltd | Information & communication | 2021 |
| Metaal Ltd | Information & communication | 2015 |
| Metaforge Gaming Ltd | Information & communication | 2025 |
| Metal Nugget Studios Ltd | Information & communication | 2026 |
| Metal-Blast Property Ltd | Real estate | 2023 |
| Metalblast Limited | Manufacturing | 1981 |
| Metalway Industries Limited | Manufacturing | 2025 |
| Metaphaura Ltd | Administrative & support | 2016 |
| Metasyde Ltd | Information & communication | 2022 |
| Metec Limited | Real estate | 2005 |
| Metric Recruitment Ltd | Administrative & support | 2023 |
| Metrics Analytics Ltd | Information & communication | 2020 |
| Metrofin Limited | Transport & logistics | 1993 |
| Metta Cards Ltd | Wholesale & retail | 2025 |
| Meyers Estate Agents (Poole a) Ltd | Real estate | 2015 |
| MEZ Engineering Ltd | Professional & scientific | 2021 |
| MEZ Invest Ltd | Real estate | 2020 |
| MF Kahuma Ltd | Real estate | 2022 |
| Mfmark Limited | Wholesale & retail | 2025 |
| MG Design Ltd | Wholesale & retail | 2025 |
| MG Global Holdings Limited | Financial services | 2024 |
| Mgbs Projects Ltd | Construction | 2011 |
| MGC AI Ltd | Manufacturing | 2025 |
| MGE Boutique Ltd | Professional & scientific | 2022 |
| MGM Xxiv Properties Limited | Real estate | 2024 |
| MGZ Direct Ltd | Wholesale & retail | 2022 |
| MH Commerce Ltd | Wholesale & retail | 2025 |
| MH Digital Solutions Ltd | Professional & scientific | 2013 |
| MH Warehousing Limited | Transport & logistics | 2025 |
| MH Window Cleaning Ltd | Administrative & support | 2017 |
| MHH (Seaview) Ltd | Real estate | 2020 |
| MI Business Partner Ltd | Administrative & support | 2024 |
| MI Mondo Ltd | Manufacturing | 2017 |
| MIA Cars Limited | Wholesale & retail | 2025 |
| MIA MIA Life Ltd | Other services | 2020 |
| Mian Bablu Limited | Wholesale & retail | 2025 |
| Miappets Limited | Wholesale & retail | 2025 |
| Miau Ltd | Administrative & support | 2024 |
| MIC Renovations Ltd | Construction | 2026 |
| Michigan Pro Limited | Wholesale & retail | 2025 |
| Microkyma Limited | Professional & scientific | 2017 |
| Micron Datera Limited | Manufacturing | 2015 |
| Microsys Softtech Limited | Hospitality | 2024 |
| Midas Entertainment Limited | Arts & recreation | 2012 |
| Midchines Management (Bournemouth) Limited | Households | 2001 |
| Middle Lane Market Ltd | Hospitality | 2019 |
| Middleton Software Ltd | Information & communication | 2024 |
| Mide Janelle Ltd | Information & communication | 2025 |
| Midland House LLP | | 2009 |
| Midland Renewables (UK) Limited | Construction | 2013 |
| Midmar Power Systems Limited | Manufacturing | 2006 |
| Midmarch Limited | Professional & scientific | 2004 |
| Midnight Gaming Limited | Arts & recreation | 2013 |
| Midway Management Limited | Professional & scientific | 2014 |
| Midway Property Limited | Real estate | 2021 |