| Megasweet Ltd | Manufacturing | 2024 |
| Megrose Developments Ltd | Construction | 2020 |
| Meilleur Interiors Limited | Professional & scientific | 2017 |
| Mekaso Enterprises Ltd | Transport & logistics | 2016 |
| Melanie Louise Ltd | Health & social care | 2025 |
| Melbury (Branksome Park) Limited | Households | 1970 |
| Melbury House Management Limited | Households | 2001 |
| Melford Court Freehold Limited | Professional & scientific | 2004 |
| Meliora Inns Ltd | Hospitality | 2021 |
| Melissa Hague Coaching Conversations Ltd | Professional & scientific | 2022 |
| Melissa Valeting Limited | Wholesale & retail | 2016 |
| Melk BCP Properties Limited | Construction | 2025 |
| Melk Limited | Real estate | 2011 |
| Mellio PUB Limited | Hospitality | 2025 |
| Melrose Court RTM Company Limited | Households | 2008 |
| Melting World Ltd | Real estate | 2021 |
| Meluris Ltd | Other services | 2020 |
| Melville Gardens Residents Limited | Households | 2003 |
| Membrane Technology Systems Limited | Construction | 2002 |
| Memo BUL Trading Ltd | Construction | 2013 |
| Memo RO Limited | Transport & logistics | 2019 |
| Menace Performance Ltd | Construction | 2015 |
| Mendes DE Oliveira Limited | Hospitality | 2024 |
| Mendex Limited | Information & communication | 2026 |
| Mental Minds Ltd | Professional & scientific | 2026 |
| Meraki Beach Ltd | Wholesale & retail | 2021 |
| Meraki Health Yorkshire Ltd | Health & social care | 2023 |
| Meraki Tattoo Lounge Ltd | Other services | 2019 |
| Merchant & Supply Co. Limited | Wholesale & retail | 2022 |
| Merchants' Place (Poole) NO.1 Residents Company Limited | Households | 1986 |
| Merchants' Place (Poole) NO.2 Residents Company Limited | Households | 1986 |
| Meridian Alliance Limited | Manufacturing | 1996 |
| Meridian Fire and Safety Ltd | Public administration | 2025 |
| Meridian Security Ltd | Administrative & support | 2019 |
| Merit Print U.K. Limited | Information & communication | 1988 |
| Merlin Performance Limited | Wholesale & retail | 2024 |
| Merlion Asset Holdings Limited | Financial services | 2023 |
| Merlion Equities (Cheswick) Ltd | Administrative & support | 2015 |
| Merlion Equity Holdings Ltd | Financial services | 2017 |
| Merlion Homes Limited | Real estate | 2017 |
| Merlion Housing Association Ltd | Administrative & support | 2010 |
| Merlion Services Ltd | Administrative & support | 2009 |
| Mermaid Mixers Limited | Manufacturing | 2022 |
| Merox Limited | Manufacturing | 2014 |
| Merrion Court (Management) Limited | Households | 1977 |
| Merrion Developments Limited | Construction | 1999 |
| Merrydene (Management) Company Limited | Extraterritorial | 1989 |
| Merryfield Court Self Management Company Limited | Households | 2000 |
| Merryvale Court Limited | Households | 2006 |
| Mersham Properties Limited | Real estate | 1998 |
| Mertaren Limited | Real estate | 2026 |
| Merton Court (Bournemouth) Management Company Limited | Households | 1988 |
| Mertonur Limited | Wholesale & retail | 2018 |
| Merv Hannam Limited | Wholesale & retail | 2011 |
| Mesopotamian Kurds Ltd | Health & social care | 2022 |
| Met-Italia Limited | Hospitality | 2018 |
| Metabolise Limited | Manufacturing | 2010 |
| Metacodec Biosciences Ltd | Professional & scientific | 2025 |
| Metacor Ltd | Health & social care | 2023 |
| Metal Fatigue Limited | Other services | 2018 |
| Metal Trading UK Limited | Wholesale & retail | 2000 |
| Metalex ACP Limited | Wholesale & retail | 2005 |
| Metalex Holdings Limited | Other services | 2018 |
| Metalex Products Holdings Limited | Financial services | 2025 |
| Metalex Products Limited | Other services | 1993 |
| Metalex Properties Holdings Limited | Financial services | 2025 |
| Metalloys Investments Ltd | Wholesale & retail | 2016 |
| Metamarvel Limited | Real estate | 2025 |
| Metanoia.Ai Ltd | Professional & scientific | 2026 |
| Method House Limited | Information & communication | 2014 |
| Metro Market Ltd | Wholesale & retail | 2016 |
| Metroball Limited | Real estate | 2002 |
| Metroimprovements Ltd | Construction | 2025 |
| Mexbourne Limited | Health & social care | 2012 |
| Meydan Properties Ltd | Real estate | 2022 |
| Meyrick CM Ltd | Administrative & support | 2025 |
| Meyrick Court (Management) Limited | Households | 1973 |
| Meyrick Gate Freehold Limited | Households | 2017 |
| Meyrick Holdings Limited | Financial services | 2017 |
| Meyrick International Limited | Wholesale & retail | 2021 |
| Meyrick Park 31 RTM Limited | Households | 2006 |
| Meyrick Park Mansions Limited | Households | 1961 |
| Meyrick Real Estate Limited | Real estate | 2017 |
| Meyvn Limited | Professional & scientific | 2023 |
| Mezzanotte Ltd | Information & communication | 2024 |
| MF Cars Dorset Ltd | Transport & logistics | 2018 |
| MF Marine Ltd | Manufacturing | 2023 |
| MFS Construction Limited | Construction | 2004 |
| MG Activities & Leisure Limited | Education | 2021 |
| MG Freehold Limited | Real estate | 2024 |
| MGB Commercial & Bridging Finance Ltd | Financial services | 2019 |
| MGK Limited | Financial services | 2023 |
| MGK Therapies Ltd | Health & social care | 2015 |
| MHD Ezati's Constructions Limited | Construction | 2025 |
| MI Marine Limited | Manufacturing | 2020 |
| MI Nursing Services Ltd | Health & social care | 2023 |
| Miah Takeaways Ltd | Hospitality | 2026 |
| Miami Court Management Limited | Households | 1987 |
| Miami Market Ltd | Wholesale & retail | 2025 |
| Mica Productions Ltd | Administrative & support | 2023 |