| MIB Collective Ltd | Wholesale & retail | 2025 |
| MIB Renovation Limited | Construction | 2023 |
| Miba Plus Ltd | Construction | 2024 |
| MIC Finder Ltd | Wholesale & retail | 2024 |
| Mica Assets Limited | Construction | 2024 |
| Michael Fahami Ltd | Health & social care | 2006 |
| Michael Handley Recruitment Limited | Administrative & support | 2023 |
| Michael Handley Solutions Limited | Financial services | 2023 |
| Michael Kells Medical Consulting Limited | Professional & scientific | 2010 |
| Michael Middleton Films Limited | Information & communication | 2018 |
| Michael Monks Ltd | Construction | 2018 |
| Michael O'Connor Limited | Construction | 1971 |
| Michael Shwartz Construction Limited | Professional & scientific | 1998 |
| Michael Shwartz Group Limited | Extraterritorial | 2000 |
| Michael's Garden Maintenance Limited | Administrative & support | 2014 |
| MICHAEL86 Ltd | Construction | 2017 |
| Michelo Consulting Limited | Administrative & support | 2017 |
| Michnom Limited | Professional & scientific | 2014 |
| Michtony Builders Ltd | Construction | 2019 |
| Michuzi Ltd. | Hospitality | 2017 |
| Mickael's Bakehouse Limited | Other services | 2013 |
| Micol Digital Limited | Professional & scientific | 2024 |
| Micro Bubble Tech Limited | Information & communication | 2023 |
| Micro Industries Limited | Wholesale & retail | 2005 |
| Micro Pharma Ltd | Professional & scientific | 2023 |
| Microaid Projects Limited | Information & communication | 2006 |
| Microcube Limited | Information & communication | 2016 |
| Microfact Limited | Information & communication | 1998 |
| Microfast Technologies Ltd | Information & communication | 2008 |
| Microglobe Optics Limited | Wholesale & retail | 2016 |
| Microminder Cyber Security Ltd | Information & communication | 2022 |
| Microtransport Limited | Transport & logistics | 2025 |
| Microwave Vision Systems Limited | | 1987 |
| Midaas Star Limited | Professional & scientific | 2017 |
| Midas AJR Ltd | Real estate | 2021 |
| Midas Furniture Ltd | Wholesale & retail | 2021 |
| Midas Real Estate Limited | Real estate | 2021 |
| Midas Touch Collectables Limited | Wholesale & retail | 2019 |
| Middle Eight Communications Limited | Professional & scientific | 2021 |
| Middle of OUR Street Limited | Administrative & support | 2021 |
| Middle Road Barber Ltd | Other services | 2026 |
| Middle Street (Leasehold) Ltd | Real estate | 2026 |
| MIDDLE8 Live Limited | Arts & recreation | 2022 |
| Middlesex Loft & Construction Limited | Construction | 2018 |
| Middlesex Tamil Academy | Hospitality | 2012 |
| Middlesex Textiles (UK) Limited | Other services | 1996 |
| Middlesex Textiles Limited | Professional & scientific | 1969 |
| Middling Pharma Ltd | Financial services | 2020 |
| Mide Properties Ltd | Real estate | 2022 |
| Midland Court Ltd | Real estate | 2012 |
| Midland Venture Limited | Hospitality | 2019 |
| Midlands Builders & Plumbers Merchants Ltd | Wholesale & retail | 2015 |
| Midline Procurement Ltd | Wholesale & retail | 2024 |
| Midline Properties Ltd | Real estate | 2018 |
| Midmakuk Limited | Construction | 2020 |
| Midnight Master FIX Ltd | Wholesale & retail | 2014 |
| Midnight to SIX Ltd | Arts & recreation | 2023 |
| Midtown Solution Ltd | Construction | 2026 |
| Midwest Group Limited | Financial services | 2021 |
| Midwest Resources Solutions Limited | Water & waste | 2022 |
| Midwives in Your Pocket Ltd | Information & communication | 2017 |
| Miera Consulting Ltd | Professional & scientific | 2006 |
| Mightrip.Co.Uk Limited | Administrative & support | 2025 |
| Mightyhousewares.Com Limited | Wholesale & retail | 2013 |
| Migration Mentors Limited | Professional & scientific | 2025 |
| Miguelito Construct Ltd | Construction | 2018 |
| Miha Premium Clean Solutions Limited | Administrative & support | 2025 |
| Mihaela Beauty Concept Ltd | Other services | 2025 |
| Mihaela Hair Salon Limited | Other services | 2025 |
| Mihu Limited | Real estate | 2026 |
| MII & U Limited | Extraterritorial | 2011 |
| Miiaider Limited | Information & communication | 2025 |
| Mikaa Ltd | Hospitality | 2026 |
| Mike Bussell Limited | Construction | 2014 |
| Mike Mechanical Inspection Ltd | Professional & scientific | 2025 |
| Mike Trans Ltd | Transport & logistics | 2024 |
| Mikes Coachworks Ltd | Wholesale & retail | 2001 |
| Milad Hilli Limited | Other services | 2013 |
| Miladerma Limited | Professional & scientific | 2024 |
| Milaka Enterprise Ltd | Other services | 2012 |
| Milani Construction Limited | Construction | 2022 |
| Milano Stores Ltd. | Wholesale & retail | 2010 |
| Milanwithink Limited | Wholesale & retail | 2026 |
| Mile Civils Ltd | Transport & logistics | 2017 |
| Milebuild Limited | Real estate | 2010 |
| Miles Lodge (Harrow) Company Limited | Households | 1985 |
| Miles of Smiles Daycare Ltd | Health & social care | 2020 |
| Milestone Recruitment Limited | Administrative & support | 2017 |
| Milestone Ventures Limited | Manufacturing | 2013 |
| Mili Construction Limited | Construction | 2006 |
| Milina London Limited | Wholesale & retail | 2012 |
| Milk Audio Limited | Other services | 2017 |
| Mill Hill Autos Ltd | Wholesale & retail | 2020 |
| Mill Hill Country Club Limited | Arts & recreation | 2002 |
| Mill Meadows Childcare Limited | Health & social care | 2011 |
| Millapps Ltd | Information & communication | 2015 |
| Millarms Holding Ltd | Financial services | 2024 |
| Millarms Property Ltd | Financial services | 2024 |
| Millbank Dental Care Limited | Health & social care | 2010 |
| Millbank Holdco Ltd | Financial services | 2024 |