| Missenden Mews Limited | Households | 2017 |
| Mission Marketing Ltd | Professional & scientific | 2021 |
| Mission Sensors Ltd | Wholesale & retail | 2025 |
| Mitchell Rose Design Limited | Professional & scientific | 2016 |
| MJH Property Services Ltd | Manufacturing | 2022 |
| MJP Motor Services Limited | Wholesale & retail | 2022 |
| MK Research Limited | Professional & scientific | 2016 |
| MM Home Ltd | Real estate | 2016 |
| Mmcpr Ltd | Health & social care | 2023 |
| Mmmll Limited | Real estate | 2013 |
| Modern Classic Wire Wheels Limited | Professional & scientific | 1996 |
| Modern Nails & Beauty Beaconsfield Ltd | Other services | 2025 |
| Modern Plant Nursery Limited | Agriculture & fishing | 2014 |
| Moderncourt Limited | Real estate | 2000 |
| Moedus Ltd | Professional & scientific | 2020 |
| Mogami Limited | Health & social care | 2021 |
| Mogul.Global Ltd | Administrative & support | 2022 |
| Money Chef Limited | Professional & scientific | 2016 |
| Money Mapping Limited | Administrative & support | 2004 |
| Monster Packaging Ltd | Administrative & support | 2019 |
| Moore Wood Management Ltd | Real estate | 2022 |
| MORE4APPS UK Limited | Information & communication | 2007 |
| Morgan Corporate Communications Ltd | Professional & scientific | 2013 |
| Morgan Krantz Limited | Other services | 2025 |
| Morina Estates Ltd | Real estate | 2017 |
| Morpheus Data Limited | Information & communication | 2016 |
| Morse Funeral Services Ltd | Other services | 2020 |
| Moshpyt Ltd | Information & communication | 2022 |
| Motor Wheel Service and Repair Company Limited | Professional & scientific | 1996 |
| Motor Wheel Service International Limited | Wholesale & retail | 1984 |
| Motor Wheel Service Limited | Wholesale & retail | 1983 |
| Motu Limited | Administrative & support | 1999 |
| Mount Kellet Limited | Real estate | 2007 |
| Mountain Warlock Brewing Ltd | Manufacturing | 2023 |
| Movers & Shakers Limited | Professional & scientific | 1999 |
| Movers & Shakers Property Breakfast Club Limited | Arts & recreation | 1997 |
| Movers & Shakers Property Networking Club Limited | Arts & recreation | 2004 |
| Movers & Shakers Regional Limited | Extraterritorial | 2013 |
| MOY Consulting Limited | Other services | 2024 |
| MPP Tech Ltd | Information & communication | 2015 |
| MPS & BBI International Limited | Administrative & support | 1997 |
| MPS & Business to Business Group Limited | Financial services | 2004 |
| MR John Paul Murphy Consultant Orthopaedic Ltd | Health & social care | 2024 |
| Mreps Trustees (NO 90) Limited | Professional & scientific | 2003 |
| MRG Lighting Limited | Other services | 2023 |
| MRP Advisory Ltd | Professional & scientific | 2013 |
| MS Marine Consultants Limited | Professional & scientific | 2022 |
| MS Property Investments & Holdings Limited | Real estate | 2025 |
| Mshb Consulting Ltd | Professional & scientific | 2025 |
| MTC Nowocien Limited | Transport & logistics | 2016 |
| MTL Studio Ltd | Manufacturing | 2025 |
| Mulberry's of Beaconsfield (Beauty) Ltd | Other services | 2016 |
| Mumsformums Limited | Other services | 2014 |
| Music and Sound Awards Ltd | Professional & scientific | 2012 |
| MVS Building Limited | Construction | 2018 |
| Mwaves Limited | Professional & scientific | 2005 |
| My Builder (UK) Limited | Construction | 2003 |
| My Online Marketer Limited | Professional & scientific | 2015 |
| My Product Path Limited | Administrative & support | 2021 |
| My Wealth Cloud Ltd | Information & communication | 2011 |
| My-Wardrobe Limited | Wholesale & retail | 2013 |
| Mykite Limited | Professional & scientific | 2009 |
| Mysterious Movies Ltd | Administrative & support | 2010 |
| MZA Acoustics Limited | Professional & scientific | 2017 |
| MZA Consulting Engineers Limited | Professional & scientific | 2014 |
| N & G Palmer Property Co Ltd | Real estate | 2015 |
| N a Brown Holdings Ltd | Real estate | 2018 |
| N K Developments (Englefield Green) Ltd | Construction | 2024 |
| N K Developments (Lane END) Ltd | Construction | 2024 |
| N K Developments (Send) Ltd | Construction | 2022 |
| N K Partnerships Ltd | Construction | 2023 |
| N&L Advisory Limited | Professional & scientific | 2026 |
| N&Sr Investments Ltd | Real estate | 2017 |
| N.P.S Windows Ltd | Construction | 2015 |
| Naani Ltd | Information & communication | 2026 |
| Nadar Estates Limited | Real estate | 2024 |
| Naia Beach Ltd | Wholesale & retail | 2020 |
| Nascot Homes (South Road) Limited | Construction | 2016 |
| National Carers Services Ltd. | Health & social care | 2020 |
| Naughty and Nice Limited | Wholesale & retail | 2023 |
| Navajo Limited | Information & communication | 2018 |
| Navybeck Limited | Arts & recreation | 1987 |
| Ncontrol LLP | | 2009 |
| NE4TEE3 Limited | Real estate | 2013 |
| Neil Miller Associates Limited | Professional & scientific | 2016 |
| Nemenn Ltd | Extraterritorial | 2021 |
| Neptune Capital Limited | Other services | 2022 |
| Neptune Hospitality Ltd | Hospitality | 2025 |
| Nerd Origins Ltd | Information & communication | 2018 |
| Nest & Nomad Stays Ltd | Hospitality | 2026 |
| Net-Rate Limited | Wholesale & retail | 1996 |
| Netscientific UK Limited | Administrative & support | 2006 |
| Neurascalex Limited | Education | 2024 |
| Nevermore Limited | Information & communication | 2008 |
| Nevo Talent Ltd | Administrative & support | 2025 |
| New Ballerino & Co Limited | Real estate | 2007 |
| New Ballerino Consultancy Limited | Professional & scientific | 2024 |
| New Bletchley Project Ltd | Professional & scientific | 2026 |
| New Body Clinic Limited | Health & social care | 2021 |
| New ERA Project Limited | Professional & scientific | 2025 |