| Medilync Limited | Wholesale & retail | 2024 |
| Medina Laser Clinic Ltd | Wholesale & retail | 2026 |
| Medipharm Ultrasound Limited | Health & social care | 2025 |
| Mednex Limited | Wholesale & retail | 2013 |
| Mednex Property Investment Ltd | Real estate | 2025 |
| Medulla Ltd | Construction | 2015 |
| Meekail Properties Ltd | Real estate | 2025 |
| Meer Trading Ltd | Health & social care | 2025 |
| Meeran Holdings Ltd | Financial services | 2020 |
| Mefco Interiors Limited | Manufacturing | 2024 |
| Megalyfe Fitness Ltd | Arts & recreation | 2018 |
| MEH Contractors (Morden) Ltd | Construction | 2024 |
| MEH Trading Ltd | Wholesale & retail | 2016 |
| Mehmood and Sons Limited | Real estate | 2021 |
| Mehroz Sons Ltd | Wholesale & retail | 2022 |
| MEI Holds Ltd | Financial services | 2025 |
| MEI Property Investment Ltd | Real estate | 2025 |
| Meka Fact Construction Ltd | Construction | 2025 |
| Melti Gelato Ltd | Manufacturing | 2026 |
| Memory Lane Audiobooks Ltd | Information & communication | 2022 |
| Mend Handyman Services Ltd | Administrative & support | 2022 |
| Mentive Capital Limited | Information & communication | 2026 |
| Menu Support Limited | Administrative & support | 2026 |
| Meridian Crest Advisory Ltd | Administrative & support | 2026 |
| Meridian Global Health Ltd | Health & social care | 2026 |
| Meridian Recruitment Ltd | Administrative & support | 2026 |
| Merit Supplies Ltd | Wholesale & retail | 2018 |
| Merit Ways Limited | Wholesale & retail | 2018 |
| Merton Crash Repairs Ltd | Wholesale & retail | 2011 |
| Merton Handball Club Ltd | Education | 2024 |
| Merton Health CIC | Health & social care | 2015 |
| Merton Mavericks Ltd | Arts & recreation | 2024 |
| Merton Mencap | Health & social care | 2006 |
| Merton Tuition Centre Ltd | Education | 2024 |
| Mesh Healthcare Limited | Health & social care | 2015 |
| Messrs Aask Solicitors Limited | Professional & scientific | 2018 |
| Metaflex Sign Systems UK Ltd | Manufacturing | 2024 |
| Metro Easy Shopping Limited | Wholesale & retail | 2013 |
| Metronome Life Limited | Hospitality | 2020 |
| Metropole Security & FM Ltd | Administrative & support | 2024 |
| Metropolis Movers Ltd | Transport & logistics | 2026 |
| Metropolitan Driving School Limited | Education | 2018 |
| Mewna Ltd | Wholesale & retail | 2026 |
| Mezan Unity Ltd | Hospitality | 2026 |
| MFC London Ltd | Transport & logistics | 2024 |
| MFC One Ltd | Wholesale & retail | 2019 |
| Mfwr Limited | Administrative & support | 2022 |
| MG Recruitment LP | | 2009 |
| MG Triumph Ltd | Construction | 2016 |
| MGK Contractors Ltd | Construction | 2014 |
| MGN Hire Ltd | Wholesale & retail | 2015 |
| MGN Management Services Ltd | Wholesale & retail | 2015 |
| MGT Solutions Limited | Information & communication | 2014 |
| MH Global Enterprise Ltd | Wholesale & retail | 2024 |
| MH UK Property Investment Ltd | Real estate | 2019 |
| MHD Trading Ltd | Transport & logistics | 2023 |
| Mhsa Ltd | Real estate | 2017 |
| Mhtt Trading Ltd | Administrative & support | 2016 |
| Mi-Kalooji Ltd | Wholesale & retail | 2020 |
| Miam Trading Ltd | Transport & logistics | 2019 |
| Miaraj Limited | Hospitality | 2019 |
| Michael Kula Contractors Ltd | Construction | 2015 |
| Micro Universe Trading Company Ltd | Wholesale & retail | 2023 |
| Middlesex Assets Ltd | Construction | 2024 |
| MIG Construction Solutions Limited | Construction | 2013 |
| Miki B&A Ltd | Transport & logistics | 2024 |
| Milaved Limited | Information & communication | 2025 |
| Milela Ltd | Real estate | 2021 |
| Milka Sports Ltd | Wholesale & retail | 2007 |
| Mill Price Online Limited | Wholesale & retail | 2019 |
| Millennium Quther Car UK Limited | Wholesale & retail | 2022 |
| Million Dreams Limited | Administrative & support | 2024 |
| Millstream Penthouse Systems Limited | Manufacturing | 1998 |
| Milton Keynes Property Investment Private Limited | Real estate | 2015 |
| MIM Management Holdings Ltd | Financial services | 2025 |
| MIM Management Ltd | Real estate | 2025 |
| Mimmi Morris Ltd | Health & social care | 2017 |
| Mind Education Ltd | Education | 2019 |
| Mind Investment Limited | Real estate | 2023 |
| Mind the Puff Waterloo Ltd | Wholesale & retail | 2025 |
| Mindash Tech Limited | Information & communication | 2025 |
| Mindspace Outsourcing Ltd | Professional & scientific | 2014 |
| Mingop Limited | Administrative & support | 2015 |
| Mini Sothi's Holdings Ltd | Financial services | 2026 |
| Mini Treasures Nursery Ltd | Education | 2009 |
| Minis Netball Ltd | Arts & recreation | 2021 |
| Ministry of Ice Ltd | Manufacturing | 2025 |
| MIR London Trading Ltd | Transport & logistics | 2017 |
| MIR Services Ltd | Transport & logistics | 2019 |
| MIR Technologies Ltd | Administrative & support | 2017 |
| Mir's Rooster Ltd | Hospitality | 2020 |
| Mira Prospera Ltd | Administrative & support | 2025 |
| Mirat Network Limited | Professional & scientific | 2025 |
| Mirha E-Commerce Ltd | Wholesale & retail | 2026 |
| Mirha Investments Limited | Professional & scientific | 2018 |
| Mirha Property Maintenance Ltd | Construction | 2024 |
| Mirza Digital Ltd | Wholesale & retail | 2025 |
| Mirza Group London Ltd | Real estate | 2021 |
| Mister Concrete Limited | Manufacturing | 2015 |
| Mittal & Bansal and Associates Ltd | Health & social care | 2018 |