| MEG Crystal Ltd | Administrative & support | 2025 |
| Meico Shop Ltd | Manufacturing | 2024 |
| Melamick Commerce Solution Ltd | Wholesale & retail | 2024 |
| Melbourne Bidco Limited | Financial services | 2021 |
| Melbourne Holdco Limited | Financial services | 2021 |
| Melbourne Midco Limited | Financial services | 2021 |
| Melbourne Topco Limited | Financial services | 2021 |
| Meliora London Collection Limited | Wholesale & retail | 2022 |
| Melisoles Ltd | Wholesale & retail | 2025 |
| Mellow Candle Co. Ltd | Manufacturing | 2025 |
| Melon Renovations Limited | Construction | 2019 |
| Mendeco Limited | Professional & scientific | 2015 |
| Menmoney Limited | Wholesale & retail | 2024 |
| Menzfeld Technology Services Ltd | Information & communication | 2025 |
| Menzies Medical Communications Limited | Professional & scientific | 2024 |
| Mepro Removals Ltd | Transport & logistics | 2025 |
| Mercury Bidco Globe Limited | Financial services | 2023 |
| Mercury Midco I Limited | Financial services | 2023 |
| Mercury Midco II Limited | Financial services | 2023 |
| Mercury Rising Limited | Real estate | 2023 |
| Mercymade Limited | Health & social care | 2024 |
| Merepress Limited | Wholesale & retail | 2008 |
| Meri Jaan Limited | Wholesale & retail | 2026 |
| Meridian Holdings Limited | Real estate | 2025 |
| Meridian Solutions & Investments Limited | Professional & scientific | 2024 |
| Merjan Moters Limited | Wholesale & retail | 2020 |
| Merkaz Letoras Hachassidus Ltd | Other services | 2020 |
| Merler Ltd | Real estate | 2018 |
| Merlin Care Ltd | Wholesale & retail | 2010 |
| Merlin II LP | | 2016 |
| Merline Certs Limited | Construction | 2020 |
| Merline Limited | Construction | 2019 |
| Merlyn Electronics Limited | Manufacturing | 2000 |
| Merseyside BSD Ltd | Real estate | 2026 |
| Mersic - Middle East Research and Social Investment Consultancy Ltd. | Professional & scientific | 2015 |
| Merthyr Real Estates Ltd | Other services | 2021 |
| Mesila Manchester Ltd | Other services | 2021 |
| Mesukim Ltd | Health & social care | 2014 |
| Meta Trend Fashion Limited | Transport & logistics | 2022 |
| Metabee Holding Company Ltd | Financial services | 2023 |
| Metal Shredder Limited | Wholesale & retail | 2010 |
| Metalmaster Structures Ltd | Manufacturing | 2025 |
| Methven UK Limited | Wholesale & retail | 2007 |
| Metriix Limited | Information & communication | 2025 |
| Metro E Limited | Real estate | 2016 |
| Metro Stays Limited | Health & social care | 2019 |
| Metropolis Investments Ltd | Construction | 2010 |
| Mettler-Toledo Capital (UK) Limited | Financial services | 2023 |
| Mettler-Toledo Finance (UK) 2 Limited | Financial services | 2023 |
| Mettler-Toledo Safeline Limited | Manufacturing | 1988 |
| Meyagates Limited | Real estate | 2018 |
| Meyer Crown Holdings Ltd | Financial services | 2023 |
| MF Innovations Ltd | Information & communication | 2026 |
| MG Builders MCR Ltd | Construction | 2023 |
| MG Estates MCR Ltd | Real estate | 2026 |
| MG Home Ltd | Real estate | 2025 |
| MG Joinery Ltd | Construction | 2019 |
| MGC International Limited | Administrative & support | 2016 |
| MGD (NW) Ltd | Construction | 2022 |
| MGI Newcastle Limited | Real estate | 2025 |
| MGM Accountants Ltd | Professional & scientific | 2012 |
| MGN World Travel Ltd | Transport & logistics | 2026 |
| MH Civils Ltd | Administrative & support | 2015 |
| MH Global Consulting Ltd | Administrative & support | 2020 |
| MHC Catering Ltd | Hospitality | 2024 |
| MHK Renewables Ltd | Professional & scientific | 2024 |
| MHP Trading Ltd | Wholesale & retail | 2022 |
| MHT Services Ltd | Wholesale & retail | 2019 |
| Mian Fashions Nationwide Ltd | Wholesale & retail | 2019 |
| Mibor Tech Ltd | Construction | 2026 |
| MIC North Limited | Real estate | 2023 |
| Michael Shapiro Limited | Professional & scientific | 2023 |
| Michtom Estates Limited | Real estate | 2017 |
| Micro Delta Packaging Limited | Wholesale & retail | 2019 |
| Micro-D Limited | Wholesale & retail | 2013 |
| Microdepot Ltd | Transport & logistics | 2023 |
| Microkart Vending Ltd | Wholesale & retail | 2025 |
| Microrama Import Export Ltd | Administrative & support | 2011 |
| MID Estates Ltd | Construction | 2025 |
| Middlehill Building Ltd | Extraterritorial | 1999 |
| Middlesbrough Timber Estate Limited | Other services | 2019 |
| Middlesbrough Timber Estate NO.2 Limited | Other services | 2019 |
| Middstock Estates Limited | Other services | 2022 |
| Middstock Holdings Limited | Other services | 2022 |
| Midgeland Properties Limited | Real estate | 2016 |
| Midland Estate Ltd | Professional & scientific | 2000 |
| Midlands Screen Acting School Limited | Arts & recreation | 2023 |
| Midwest Estates (Manchester) Limited | Professional & scientific | 2002 |
| Midwest Solutions Limited | Wholesale & retail | 2017 |
| MIG Transport Ltd | Transport & logistics | 2019 |
| Mighty & KIN Ltd | Professional & scientific | 2005 |
| Migration, Multicultural and Multidimensional Poverty Advice M3PA UK CIC | Other services | 2026 |
| Mikaray Ltd | Health & social care | 2025 |
| Miki Makeup & Co Ltd | Other services | 2017 |
| Mikkume Consultants Ltd | Professional & scientific | 2024 |
| Mikos Luxury Home Limited | Real estate | 2025 |
| Milecastle Properties Limited | Real estate | 2021 |
| Milestone TV Limited | Information & communication | 2019 |
| Military Range Ltd | Wholesale & retail | 2016 |
| Milk for Health Ltd | Hospitality | 2024 |