| Mullan Partnership Limited | Administrative & support | 2010 |
| Mullens Ltd | Wholesale & retail | 2026 |
| Mullvar Ltd | Information & communication | 2025 |
| Multi Manor Ltd | Construction | 2024 |
| Multi-Image Limited | Administrative & support | 1998 |
| Multichoice Logistics Limited | Transport & logistics | 2024 |
| Multicraft 4 YOU Limited | Construction | 2021 |
| Multimount Limited | Manufacturing | 2024 |
| Multiplay Activities Limited | Arts & recreation | 2016 |
| Multiple Access Communications (EOT) Limited | Professional & scientific | 2025 |
| Multiple Access Communications Limited | Professional & scientific | 1986 |
| Multiply Consulting Limited | Professional & scientific | 2022 |
| Multiquest (UK) Limited | Information & communication | 1996 |
| Multitools Ltd | Other services | 2008 |
| Multivilla Limited | Households | 2000 |
| Mumford Marine Services Limited | Professional & scientific | 2025 |
| Munce Holdings Limited | Professional & scientific | 2019 |
| Munchd Properties Limited | Real estate | 2021 |
| Munchiies Ltd | Hospitality | 2025 |
| Munday Capital Ventures Ltd | Professional & scientific | 2023 |
| Munetsi Legacy Ltd | Wholesale & retail | 2025 |
| Munimax Ltd | Wholesale & retail | 2025 |
| Munnan and Co Limited | Professional & scientific | 2022 |
| Muntenia CS LLP | | 2020 |
| Murarz Limited | Construction | 2017 |
| Murderedformoney Ltd | Arts & recreation | 2021 |
| Murp Ltd | Real estate | 2024 |
| Murray Event Management Ltd | Professional & scientific | 2026 |
| Musa Distribution Limited | Administrative & support | 2024 |
| Muscle APE Ltd | Education | 2018 |
| Muscle UP Gym Ltd | Arts & recreation | 2015 |
| Muse Coffee Company Limited | Hospitality | 2020 |
| Muse Corp Limited | Professional & scientific | 2022 |
| Muse Soton Limited | Hospitality | 2021 |
| Musfirah Muhsin Traders Limited | Wholesale & retail | 2025 |
| Music in the City CIC | Administrative & support | 2025 |
| Mustang Sallys Limited | Other services | 1997 |
| Mustang Survival UK Ltd | Wholesale & retail | 2025 |
| Musty District Ltd | Health & social care | 2019 |
| Muted EST 2025 Ltd | Wholesale & retail | 2025 |
| Muttees Ltd | Health & social care | 2017 |
| Muuvo Commercial Limited | Professional & scientific | 2025 |
| Muuvo Limited | Administrative & support | 2019 |
| Muça Interiors Ltd | Construction | 2025 |
| MV Consultation Services Ltd | Professional & scientific | 2019 |
| Mvmsystem Limited | Information & communication | 2009 |
| Mvnl Group Ltd | Financial services | 2025 |
| MVP Collective Limited | Information & communication | 2025 |
| Mvsicare Limited | Public administration | 2022 |
| MW Bakery Limited | Wholesale & retail | 2016 |
| MW Concepts Limited | Construction | 2018 |
| MW Cooke Properties Limited | Real estate | 2025 |
| MW Dog Grooming Ltd | Agriculture & fishing | 2023 |
| MW Hospitalities Limited | Hospitality | 2020 |
| MW Rice Ltd | Wholesale & retail | 2024 |
| Mwag Services Ltd | Construction | 2023 |
| Mwila Limited | Administrative & support | 2019 |
| Mwja Finishing Ltd | Construction | 2017 |
| MWQ Properties Limited | Real estate | 2016 |
| Mwtc Ltd | Information & communication | 2023 |
| MWW Holdings Ltd | Real estate | 2024 |
| MX8 Limited | Professional & scientific | 2023 |
| MXM Construction Ltd | Construction | 2019 |
| My Airport Guys Limited | Transport & logistics | 2021 |
| My Building Solutions Limited | Construction | 2022 |
| My Check Call Limited | Information & communication | 2025 |
| My City Estates Limited | Real estate | 2019 |
| My Dubai Ltd | Hospitality | 2026 |
| My Fibre Holdings Limited | Financial services | 2024 |
| My Fibre Limited | Professional & scientific | 2013 |
| My Football Shirt Auction Ltd | Wholesale & retail | 2024 |
| My Health Revolution Ltd | Health & social care | 2018 |
| My Mindful Self CIC | Health & social care | 2026 |
| My New Bathroom Ltd | Construction | 2021 |
| My Pottery Limited | Arts & recreation | 2019 |
| My Red Border Ltd | Wholesale & retail | 2019 |
| My Ride Company Limited | Transport & logistics | 2013 |
| My Self - Love Supply Ltd | Education | 2024 |
| My Site Passwords Limited | Information & communication | 2015 |
| My Square 2 Ltd | Real estate | 2025 |
| My Superstore Ltd. | Wholesale & retail | 2015 |
| My Sweet Shack Ltd | Wholesale & retail | 2023 |
| My Trade People LP | | 2011 |
| My Trend Global Ltd | Wholesale & retail | 2018 |
| My Trusted Electrical Limited | Manufacturing | 2024 |
| My VIP Card Limited | Other services | 2019 |
| My Way to Go Limited | Other services | 2025 |
| MYA Property Limited | Construction | 2006 |
| Myca Communications Ltd | Information & communication | 2013 |
| Mycruise UK Limited | Administrative & support | 2023 |
| Myevcp Limited | Administrative & support | 2021 |
| Myfitlife Ltd | Arts & recreation | 2020 |
| Myfundingpartner Limited | Financial services | 2010 |
| MYK Marshall Auto Diagnostic Limited | Wholesale & retail | 2021 |
| Myonehealth Ltd | Health & social care | 2025 |
| Mypad Homes Ltd | Construction | 2022 |
| Myreen Young Skincare Limited | Manufacturing | 2011 |
| Mysalesbox Ltd | Information & communication | 2015 |
| Mystery (Southampton) Limited | Hospitality | 2005 |
| Mystic Property Ltd | Real estate | 2014 |