| Mimuno Ltd | Information & communication | 2022 |
| Mindless Intelligence Ltd | Information & communication | 2019 |
| Minewell Ltd | Professional & scientific | 2024 |
| Minewproperty Limited | Real estate | 2022 |
| Minhal Healthcare Limited | Health & social care | 2013 |
| Mini Me's Preschool Limited | Education | 2006 |
| Mini Miracles Montessori at ST Faith's Limited | Health & social care | 2025 |
| Mini Miracles Montessori at ST Paul's Limited | Health & social care | 2025 |
| Mini Miracles Montessori Limited | Health & social care | 2019 |
| Mint & Matcha Limited | Hospitality | 2025 |
| Mira Metrics Research Ltd | Extraterritorial | 2012 |
| Miracle Commercial Ltd | Administrative & support | 2021 |
| Mistrydesign Limited | Arts & recreation | 2017 |
| Mizen ( Uxbridge Road ) Limited | Real estate | 2019 |
| Mizen Capital Limited | Real estate | 2019 |
| Mizen Land Limited | Real estate | 1993 |
| MJP Ventures Ltd | Financial services | 2021 |
| MK Glass Limited | Construction | 2022 |
| Mkda London Limited | Construction | 2016 |
| MKJ Accountants Limited | Professional & scientific | 2022 |
| MKM 13 Limited | Information & communication | 2017 |
| Mkmhealthcare Limited | Health & social care | 2006 |
| ML Management Consulting Ltd | Professional & scientific | 2024 |
| Mlenterpricess Ltd | Wholesale & retail | 2026 |
| MM Global Corp Ltd | Wholesale & retail | 2022 |
| MM Multiservices Ltd | Construction | 2018 |
| MMD 1 Ltd | Administrative & support | 2017 |
| MMP Property Investments Limited | Real estate | 2021 |
| MMT Catering Services Ltd | Manufacturing | 2026 |
| MNK Consultancy Ltd | Information & communication | 2018 |
| Mnproperties Ltd | Hospitality | 2007 |
| MO Tiling Limited | Construction | 2023 |
| Mobile & Vape Shop Ltd | Wholesale & retail | 2025 |
| Mocachino Limited | Hospitality | 2025 |
| Modest Dreams Ltd | Wholesale & retail | 2019 |
| Mody Khana Ltd | Health & social care | 2020 |
| Moghal Foods Brighton Ltd. | Hospitality | 2025 |
| Mohayyuddin Group Ltd | Information & communication | 2026 |
| Mohit Group Ltd | Real estate | 2024 |
| Moira Online Ltd | Wholesale & retail | 2022 |
| Mole Hole Limited | Professional & scientific | 2025 |
| Momentum Influencer Management Ltd | Professional & scientific | 2025 |
| Momin Construction Ltd | Construction | 2024 |
| Montesolaro Films Limited | Information & communication | 2024 |
| Mood Movement Ltd | Arts & recreation | 2021 |
| Moonlight Chaat House Ltd | Hospitality | 2026 |
| More House TW7 RTM Company Limited | Households | 2020 |
| Morgan Practice Limited | Health & social care | 2023 |
| Most Valuable Ltd | Manufacturing | 2024 |
| Motech Limited | Professional & scientific | 2013 |
| Motiveorder Consultants Limited | Information & communication | 1992 |
| Motocraft Service Ltd | Manufacturing | 2016 |
| Moving Forward Healthcare Limited | Health & social care | 2023 |
| Movo Construction Ltd | Construction | 2018 |
| Moxie Enterprises Limited | Wholesale & retail | 2020 |
| Mpharms Limited | Real estate | 2009 |
| MR Build Limited | Construction | 2021 |
| MR Landscapes (Surrey) Limited | Administrative & support | 2015 |
| MR Messy Ltd | Other services | 2022 |
| MS Audiology Ltd | Other services | 2024 |
| MSB Construction Limited | Construction | 2016 |
| MSJ Future Limited | Other services | 2020 |
| MSS Building Contracting Ltd | Construction | 2021 |
| Mssk Associates Limited | Construction | 2015 |
| MST Coaching Services Ltd | Other services | 2025 |
| Mstl Ltd | Transport & logistics | 2014 |
| Mulholland Furniture Ltd | Manufacturing | 2018 |
| Multicultural & Ethnic Media Sales Limited | Professional & scientific | 2003 |
| Multicultural Urban Design Ltd. | Construction | 2005 |
| Munday.Space Ltd | Arts & recreation | 2022 |
| Munna London Ltd | Wholesale & retail | 2024 |
| MUR Properties Limited | Financial services | 2018 |
| Murphy & Pycroft Ltd | Professional & scientific | 2018 |
| Murray (Productions) Limited | Manufacturing | 1972 |
| Murray Engineering Co. (Hayes) Limited | Wholesale & retail | 1984 |
| Murree Care Home Limited | Health & social care | 2009 |
| Muse & Mirror Limited | Professional & scientific | 2025 |
| Music Motion Productions Limited | Arts & recreation | 2004 |
| Mustafa Baasha Ltd | Extraterritorial | 2015 |
| Mustbebonkers Ltd | Wholesale & retail | 2004 |
| MVS Express Logistic Ltd | Transport & logistics | 2020 |
| MW Training Ltd | Arts & recreation | 2016 |
| My Electrician Limited | Construction | 2006 |
| My EV Ltd | Construction | 2003 |
| My Home Design and Build Limited | Construction | 2019 |
| My Home Infra Limited | Construction | 2025 |
| My Home Supply Limited | Construction | 2025 |
| My Salon Ltd | Other services | 2013 |
| Myct Transport Ltd | Transport & logistics | 2024 |
| Myha Chauffeurs Ltd | Transport & logistics | 2025 |
| Myhero Ltd | Information & communication | 2021 |
| Mykola Kachmar Limited | Real estate | 2023 |
| MZ Sporting Agency Limited | Professional & scientific | 2022 |
| N & L Food Supply Ltd | Wholesale & retail | 2025 |
| N S Niru Trading Ltd | Wholesale & retail | 2014 |
| NAF Electricals Ltd | Other services | 2013 |
| Nafees Gallery Limited | Wholesale & retail | 2025 |
| Nags Homes Ltd | Real estate | 2022 |
| Nahal Holdings Ltd | Real estate | 2015 |
| Nahal West Four Ltd | Real estate | 2018 |