| MC Property Development Limited | Real estate | 2018 |
| MC Property Services Ltd | Real estate | 2022 |
| MC Visual Styling Limited | Professional & scientific | 2016 |
| MCA Tiling Ltd | Construction | 2021 |
| Mccaffrey Football Investment Group Limited | Arts & recreation | 2024 |
| Mccleery Consulting Ltd | Professional & scientific | 2012 |
| Mcgi Ltd | Professional & scientific | 2017 |
| Mchl Limited | Construction | 2023 |
| Mckeever Consulting Limited | Professional & scientific | 2014 |
| MCV Trans Limited | Transport & logistics | 2017 |
| MD Taxi Hire Ltd | Other services | 2016 |
| Md&D Limited | Administrative & support | 1999 |
| Mdbrunch Limited | Arts & recreation | 2021 |
| Mddrywall Ltd | Construction | 2014 |
| MDM International Corporation Ltd | Administrative & support | 2017 |
| MDS Capital Ltd | Financial services | 2026 |
| MDS Mentoring Program CIC | Education | 2023 |
| Mead Lifestyle Ltd | Wholesale & retail | 2025 |
| MEC Global Healthcare Limited | Public administration | 2023 |
| Mechinah Golders Green Limited | Administrative & support | 2009 |
| Medbonne Limited | Administrative & support | 2016 |
| Medclick Limited | Professional & scientific | 2021 |
| Medengineering Limited | Professional & scientific | 2026 |
| Media V4 Limited | Information & communication | 2017 |
| Mediacity Limited | Information & communication | 2007 |
| Medical and Orthopaedic Services Limited | Health & social care | 2010 |
| Mediconnect Recruitment Limited | Administrative & support | 2003 |
| Medics Herts and Essex Ltd | Health & social care | 2025 |
| Medikyle Ltd | Health & social care | 2022 |
| Mediterranean (Norwich) Ltd | Hospitality | 2018 |
| Medly Limited | Real estate | 2014 |
| Medwriter Limited | Information & communication | 2010 |
| Meezan Consultancy Ltd | Real estate | 2025 |
| Mega Events / Travel / Music Holdings Limited | Other services | 2015 |
| Mega Events/ Travel/ Music Ltd | Administrative & support | 2013 |
| Mega Property Holdings Limited | Real estate | 2020 |
| Megacity Solutions Ltd | Construction | 2012 |
| Mehdi International Ltd | Professional & scientific | 2024 |
| Meica Project Services Ltd | Administrative & support | 2010 |
| Melana Capital Limited | Financial services | 2013 |
| Melin Enterprises Ltd | Financial services | 2018 |
| Melissa Wyndham Limited | Other services | 1985 |
| Melview Properties Limited | Construction | 1993 |
| MEN at Work Facilities Ltd | Construction | 2026 |
| Mensor Limited | Professional & scientific | 2003 |
| Merchav Limited | Real estate | 2024 |
| Merciless Ltd | Wholesale & retail | 2019 |
| Merged Beauty Limited | Administrative & support | 2021 |
| Meridian South Developments LLP | | 2009 |
| Meridian South Limited | Construction | 2013 |
| Merit Events Ltd | Administrative & support | 2019 |
| Merkan Ltd | Hospitality | 2019 |
| Meronden Holdings Limited | Professional & scientific | 2000 |
| Meronden Limited | Construction | 1981 |
| Mesmerise Collections Ltd | Wholesale & retail | 2025 |
| Metalex Metalworks Ltd | Manufacturing | 2012 |
| Metalytics Limited | Information & communication | 2022 |
| Method Wealth Management Limited | Financial services | 2021 |
| Metropol Facilities Limited | Administrative & support | 2021 |
| Mettle MAN Ltd | Wholesale & retail | 2020 |
| Metyus Ltd | Hospitality | 2019 |
| Mexx Properties Limited | Real estate | 2009 |
| Meyler Interiors Limited | Construction | 2014 |
| Meze Kebab Ltd | Hospitality | 2018 |
| Mezevi Limited | Hospitality | 2024 |
| MF Programmes Ltd | Information & communication | 2014 |
| MG Agency Limited | Information & communication | 2026 |
| MG Promotions Limited | Administrative & support | 1999 |
| Mgball Ltd | Information & communication | 2014 |
| MGD Transport Limited | Other services | 2004 |
| MGM Perfect Ltd | Construction | 2020 |
| MGS Kohli Investments Ltd | Real estate | 2019 |
| Mgsboc Ltd | Wholesale & retail | 2019 |
| MH Optics Ltd | Health & social care | 2015 |
| Mi-Engineer International Limited | Professional & scientific | 2023 |
| Michael Collins & Associates Limited | Administrative & support | 1987 |
| Michael Investments Ltd | Other services | 2015 |
| Michael James Real Estate Ltd | Real estate | 2016 |
| Michaels & Co Law Limited | Professional & scientific | 2014 |
| Micro Pads Limited | Administrative & support | 2021 |
| Microserf Limited | Information & communication | 1998 |
| Midas Industries Limited | Real estate | 2022 |
| Middlesex Motor Caravans Limited | Other services | 1998 |
| Midus Recruitment Ltd | Administrative & support | 2021 |
| Mighty Alpha Care Services Ltd | Health & social care | 2017 |
| Mihov Solution Ltd | Construction | 2018 |
| Mill Hill Engineering Limited | Manufacturing | 2016 |
| Mill Hill Eruv Committee | Other services | 2011 |
| Mill Hill Heavy Engineering Limited | Manufacturing | 2007 |
| Millbray Contracts Limited | Transport & logistics | 2005 |
| Millbray Holdings Limited | Professional & scientific | 2003 |
| Millbray Pallets Limited | Transport & logistics | 2003 |
| Millennials First Ltd | Real estate | 2019 |
| Millennium Lets Limited | Real estate | 2012 |
| Miller & Miller (Chemicals) Limited | Wholesale & retail | 1977 |
| Millercode Ltd | Information & communication | 2021 |
| Millercom Ltd | Financial services | 2025 |
| Milos Investments Limited | Real estate | 2019 |
| Miltonmatthew Limited | Professional & scientific | 2023 |
| Milvus Advanced Limited | Professional & scientific | 2020 |