| Moonlight Accountants Limited | Professional & scientific | 2022 |
| Moonlight Hair Salon Limited | Other services | 2011 |
| Moonstone Therapies Limited | Other services | 2022 |
| Moorehouse Properties Limited | Households | 2004 |
| Moormead Grill Ltd | Hospitality | 2026 |
| Morales & Arnone Capital Partners Limited | Real estate | 2025 |
| Morcos Group Ltd | Construction | 2026 |
| More - Oomph Limited | Professional & scientific | 2008 |
| More Capital Ltd | Financial services | 2022 |
| More With Training Limited | Information & communication | 2025 |
| Moreton and GUY Limited | Manufacturing | 2013 |
| Moreton Place Residents Company Limited | Households | 1995 |
| Morgan ST Ledger Limited | Professional & scientific | 2018 |
| Morganbuild Ltd | Construction | 2019 |
| Morina Projects Ltd | Construction | 2020 |
| Mornington Road (Norwich) Management Company Limited | Households | 2019 |
| Morrighan Ltd | Professional & scientific | 2023 |
| Mortlake Station Garage Limited | Wholesale & retail | 2008 |
| Mosaic (Felbridge) Ltd | Real estate | 2004 |
| Mosaic (Southsea) Ltd | Real estate | 2004 |
| Mosaic (Twickenham) Limited | Real estate | 2018 |
| Mosaic (Woolavington) Ltd | Real estate | 2024 |
| Mosaic Consultants Limited | Transport & logistics | 2016 |
| Mosaic Estates Ltd | Professional & scientific | 1999 |
| Moselle Avenue Limited | Professional & scientific | 2026 |
| Mospey Care Ltd | Health & social care | 2019 |
| Moss Dog Ltd | Wholesale & retail | 2025 |
| Moss PUB Company Limited | Hospitality | 2024 |
| Motion 88 Limited | Information & communication | 2014 |
| Motion Sportswear Limited | Wholesale & retail | 2026 |
| Motive Design and Advertising Limited | Professional & scientific | 2002 |
| Motorview (London) Ltd | Wholesale & retail | 2025 |
| Mottik International Limited | Water & waste | 1992 |
| Mount Sion Joinery Limited | Manufacturing | 2012 |
| Mountain Construction Limited | Construction | 1984 |
| Mountain Homes Limited | Construction | 2016 |
| Mountain Property Services Limited | Real estate | 1988 |
| Mountain Xtra Ltd | Administrative & support | 2002 |
| Mountford House Management Ltd | Households | 2016 |
| Move MEE Ltd | Administrative & support | 2013 |
| Moyster Ltd | Wholesale & retail | 2025 |
| MP Medical Services Ltd | Health & social care | 2015 |
| MPG Property Renovations Ltd | Administrative & support | 2018 |
| Mpower Partnership LLP | | 2006 |
| MPOWER1 International Limited | Information & communication | 2014 |
| Mpumelelo Limited | Health & social care | 2015 |
| MR Bishop & the Wife Pubs Limited | Hospitality | 2024 |
| MR C Chauffeurs Limited | Transport & logistics | 2013 |
| MR Matthew Limited | Wholesale & retail | 2013 |
| MR Parker Limited | Hospitality | 2024 |
| MRF International Ltd | Administrative & support | 2021 |
| Mrjury Ltd | Wholesale & retail | 2023 |
| Mrssister Ltd | Wholesale & retail | 2026 |
| MS 77 Services Ltd | Transport & logistics | 2024 |
| MS Clean Limited | Administrative & support | 2014 |
| MS Property Managment Ltd | Real estate | 2025 |
| Mscp Holdings Limited | Administrative & support | 2012 |
| Mscp Wellbeing Limited | Other services | 1992 |
| MSJ (UK) Limited | Construction | 2013 |
| MSK Flooring Limited | Construction | 2011 |
| Msqf Ltd | Wholesale & retail | 2021 |
| MSW Brothers Ltd | Real estate | 2024 |
| MT Global Commerce Ltd | Wholesale & retail | 2023 |
| MTB Building and Landscapes Limited | Professional & scientific | 2002 |
| MTD90 Ltd | Transport & logistics | 2020 |
| Mtelif Limited | Construction | 2024 |
| Mtex Services Ltd | Construction | 2021 |
| Muddy Puppy Limited | Real estate | 2022 |
| Mueller German Foods Limited | Wholesale & retail | 2015 |
| Muffin Break Harrow Ltd | Hospitality | 2024 |
| Muggy MOO COW Ltd | Education | 2011 |
| Mukolis Ltd | Wholesale & retail | 2025 |
| Mulberry Heights Freeholders Limited | Households | 2016 |
| Mullin Land Limited | Real estate | 2023 |
| Multinet Services Limited | Information & communication | 1996 |
| Multipassionate Consulting Ltd | Administrative & support | 2022 |
| Mum’S Balm Ltd | Manufacturing | 2023 |
| Mungo Props Ltd | Information & communication | 2013 |
| Munson Glassworks Ltd | Construction | 2006 |
| Music & Media Concepts Limited | Professional & scientific | 2000 |
| Music Artist Agency Ltd | Administrative & support | 2022 |
| Music Business Associates Limited | Professional & scientific | 1999 |
| Music ED Limited | Education | 2023 |
| Music Illuminated Productions Limited | Arts & recreation | 2020 |
| Music Tuition Services Ltd | Information & communication | 2019 |
| Musketeer (Holdings) Limited | Financial services | 2021 |
| Muush Ltd | Manufacturing | 2024 |
| MVD Gardening Ltd | Administrative & support | 2017 |
| MVL Design Ltd | Professional & scientific | 2020 |
| MW Electrical and Building Services Ltd | Construction | 2014 |
| MW Lift Testing and Installation Services Limited | Construction | 2026 |
| Mwa+D Ltd | Professional & scientific | 2025 |
| MXB International Ltd | Professional & scientific | 2019 |
| MXB Services Ltd | Professional & scientific | 2019 |
| My Advantage Limited | Other services | 2016 |
| My Bars Ltd | Hospitality | 2007 |
| My Kontraktor Technologies Ltd | Information & communication | 2026 |
| My Personal Agent Limited | Real estate | 2025 |
| My-Young Ltd | Professional & scientific | 2009 |
| Mylbrook Limited | Wholesale & retail | 2005 |