| Mellor Property Holdings Limited | Real estate | 2017 |
| Melodyl Limited | Professional & scientific | 2017 |
| Meluha Ventures Limited | Real estate | 2024 |
| Melville Solutions Limited | Professional & scientific | 2012 |
| Memsahib GIN Limited | Manufacturing | 2017 |
| Memsahibs Lounge Ltd | Hospitality | 2024 |
| Mendoza Academy Limited | Education | 2021 |
| Menelson Limited | Administrative & support | 2013 |
| Menlo Security Limited | Administrative & support | 2015 |
| Mental Health Worldwide Ltd | Professional & scientific | 2025 |
| Meoki Cokey Ltd | Other services | 2018 |
| Mephis Holdings (Glos) Limited | Construction | 1963 |
| Meraki Cultura Ltd | Transport & logistics | 2021 |
| Merci Food Ltd | Wholesale & retail | 2020 |
| Mercia Associates Limited | Real estate | 2024 |
| Mercia Children Services Limited | Health & social care | 2018 |
| Mercury Contracts Limited | | 2002 |
| Mercury Cost Engineering Limited | Other services | 2017 |
| Mercury Specialist Frames Limited | Manufacturing | 2003 |
| Merger (Property Management) Limited | Extraterritorial | 1997 |
| Meridian Retail Group Limited | Wholesale & retail | 2026 |
| Merit Care Limited | Health & social care | 2014 |
| Merris Consulting Ltd | Professional & scientific | 2015 |
| Mersey Vans Ltd | Wholesale & retail | 2026 |
| Merula Design Ltd | Manufacturing | 2026 |
| Mesa Systems Limited | Information & communication | 2018 |
| Meshack Healthcare Limited | Health & social care | 2022 |
| Meshscape Limited | Professional & scientific | 2022 |
| Meta Healthcare Ltd | Health & social care | 2018 |
| Metabolic Health Solutions (UK) Ltd | Health & social care | 2011 |
| Metacell Ltd | Information & communication | 2013 |
| Metals & Chemicals Technology SDN BHD Limited | Manufacturing | 2025 |
| Metas Gerente Independiente Limited | Administrative & support | 2025 |
| Metasolutions (Fire Safety Engineering) Limited | Professional & scientific | 2008 |
| Metastrategic Consulting Limited | Professional & scientific | 2020 |
| Metisblue Limited | Education | 2012 |
| Metricstream UK Limited | Information & communication | 2012 |
| Metta Media Ltd | Information & communication | 2020 |
| Metta Systems Ltd | Information & communication | 2025 |
| Metwork (UK) Limited | Financial services | 2011 |
| Mfive Traders Limited | Wholesale & retail | 2024 |
| MG Comms & Electrical Ltd | Construction | 2024 |
| MGB Ltd | Construction | 2018 |
| MGD Consulting Limited | Information & communication | 2022 |
| Mggrill Ltd | Hospitality | 2019 |
| MH Group Limited | Construction | 1996 |
| MHM Fabrications Ltd | Manufacturing | 2013 |
| MHM Road Safety Ltd | Professional & scientific | 2020 |
| MHP Design Ltd | Professional & scientific | 2008 |
| Mhqs Consulting Ltd | Professional & scientific | 2014 |
| MHS Psychology Ltd | Education | 2025 |
| MHT Property Services (SW) Limited | Real estate | 2026 |
| MI - FI Consulting Limited | Information & communication | 2007 |
| MI Beardsley Limited | Information & communication | 2013 |
| MIA & Brother's Limited | Real estate | 2022 |
| MIA Plant Hire Limited | Administrative & support | 2010 |
| Miag Education Limited | Education | 2024 |
| Miag Independent Schools Limited | Education | 2023 |
| Miag Limited | Education | 2020 |
| Miah Consulting Ltd | Administrative & support | 2019 |
| Miami Rising Ltd | Professional & scientific | 2025 |
| Miaojianing Limited | Hospitality | 2024 |
| MIB Housing Limited | Construction | 2009 |
| MIC Global Services Limited | Administrative & support | 2008 |
| Micenna Limited | Real estate | 2012 |
| Michael Scott Property Limited | Professional & scientific | 2019 |
| Michael Yeates & Partners Limited | Professional & scientific | 2024 |
| Michelle Michael Consultancy Limited | Information & communication | 2019 |
| Micmar Ltd | Real estate | 2021 |
| Micology Limited | Information & communication | 2017 |
| Micology Solutions Limited | Information & communication | 2008 |
| Microbiological Monitoring Systems Ltd. | Information & communication | 2022 |
| Microbrain Ltd | Information & communication | 2015 |
| Microensure Asia Limited | Administrative & support | 2012 |
| Microensure Holdings Limited | Administrative & support | 2012 |
| Microsoft Project Limited | Information & communication | 2025 |
| MID Alpha Services Ltd | Real estate | 2023 |
| Midas Touch Resourcing and Business Solutions Ltd | Administrative & support | 2025 |
| Midatt Developments Limited | Real estate | 2022 |
| Midatt Limited | Construction | 2016 |
| Middle Farm 4X4S Limited | Wholesale & retail | 2023 |
| Middle Stanley House Limited | Hospitality | 2018 |
| Mididoulas Limited | Health & social care | 2023 |
| Midland (Single PLY) Holdings Limited | Professional & scientific | 2008 |
| Midland (Single PLY) Roofing Limited | Construction | 1985 |
| Midland Horizon Builders Limited | Health & social care | 2021 |
| Midnet Limited | Information & communication | 2005 |
| Midway Property Developments Limited | Construction | 2020 |
| Mielcarek SEO Limited | Information & communication | 2025 |
| Mighty Brand Agency Ltd | Professional & scientific | 2007 |
| Migratum Limited | Information & communication | 2014 |
| Mihai David Limited | Transport & logistics | 2017 |
| MIK4 Solutions Limited | Professional & scientific | 2025 |
| Mike Brooks Ltd | Professional & scientific | 2012 |
| Mike Burton Properties Limited | Real estate | 2006 |
| Mike Kitchen Ltd | Hospitality | 2024 |
| Mike Lunnon Limited | Other services | 2018 |
| Mike MAC Ltd | Professional & scientific | 2012 |
| Mike MAC Photography Ltd | Professional & scientific | 2012 |
| Mike Mccrave Hunting Limited | Agriculture & fishing | 2003 |