| M Scrivens & Co Ltd | Professional & scientific | 2022 |
| M T Brydson Holdings Ltd | Financial services | 2024 |
| M&B Lettings LLP | | 2012 |
| M&B Real Estate Limited | Real estate | 2012 |
| M&D Dynamic Properties Ltd | Real estate | 2023 |
| M&J Lavender Properties Ltd | Real estate | 2025 |
| M&S Click Nest Ltd | Wholesale & retail | 2024 |
| M&S Global Mart Hub Ltd | Wholesale & retail | 2024 |
| M. J. & G. P. Sprigg Limited | Administrative & support | 2006 |
| M. Ness Limited | Manufacturing | 2006 |
| M. R. D. Limited | Transport & logistics | 1997 |
| M.A Traditional Potatoes Ltd | Hospitality | 2024 |
| M.D. Enertech Limited | Construction | 1997 |
| M.D.E.T Holdings Limited | Financial services | 2018 |
| M.D.E.T. Limited | Administrative & support | 2000 |
| M.Evans Electrical Ltd | Construction | 2023 |
| M.I.Holdings Limited | Real estate | 2004 |
| M.R. Shipping and Exports Limited | Transport & logistics | 1988 |
| M.R.J. Furnaces Limited | Manufacturing | 1995 |
| M2 Industries Ltd | Professional & scientific | 2017 |
| M3 Services Shropshire Ltd | Construction | 2022 |
| MAB Roofing & Property Maintenance Ltd | Construction | 2022 |
| Mabri Ltd | Administrative & support | 2016 |
| MAC Agencies Ltd | Wholesale & retail | 2016 |
| MAC2 Trading Ltd | Wholesale & retail | 2024 |
| Machem Capital Ltd | Financial services | 2017 |
| Machine Tool Solutions Limited | Manufacturing | 2023 |
| Macjoe Limited | Real estate | 2020 |
| Mackenzie Associates Ltd | Professional & scientific | 2016 |
| Macol Consulting Ltd | Professional & scientific | 2010 |
| MAD Strada Events Limited | Hospitality | 2022 |
| Maddox Capital Ventures Ltd | Financial services | 2024 |
| Maddox Investment Group Ltd | Financial services | 2025 |
| Made by Alari Limited | Manufacturing | 2025 |
| Madgranite Limited | Professional & scientific | 2002 |
| Madisons Tanning Boutique Limited | Other services | 2023 |
| Maga Property Ltd | Real estate | 2019 |
| Maghollies Equipment Hire Limited | Administrative & support | 2002 |
| Magic Lemonade UK Limited | Arts & recreation | 2022 |
| Magical Thinking Pictures Limited | Information & communication | 2018 |
| Magna Power EBT Ltd | Professional & scientific | 2025 |
| Magna Power Equipment Limited | Professional & scientific | 1992 |
| Magna Power Group Ltd | Financial services | 2025 |
| Magna Power Holdings Limited | Financial services | 2020 |
| Maison Derivé Ltd | Wholesale & retail | 2023 |
| Maison Thibeault Ltd | Arts & recreation | 2026 |
| Maitland Selwyn Recruitment Limited | Administrative & support | 2020 |
| Majestic Aluminium Finishing Ltd | Manufacturing | 2012 |
| Majestic Finishing Group Limited | Manufacturing | 2015 |
| Majestic Lift Installations Limited | Construction | 2012 |
| Majestic Trade Limited | Wholesale & retail | 2026 |
| Majones Law Limited | Professional & scientific | 2024 |
| Majox Capital Management Ltd | Professional & scientific | 2021 |
| MAK Recycling Ltd | Water & waste | 2016 |
| Make Yourself at Home Ltd | Real estate | 2019 |
| Makers PUB Co - the Wildmoor Oak Ltd | Hospitality | 2026 |
| Making Maths Matter Ltd | Information & communication | 2020 |
| Making Waves Swim Ltd | Arts & recreation | 2011 |
| Manhattan Cleaning Ltd | Administrative & support | 2026 |
| Manhattan Events Limited | Arts & recreation | 2013 |
| Maniacus Entertainment Limited | Arts & recreation | 2021 |
| Manicured Ltd | Other services | 2026 |
| Manley Design and Construction Limited | Construction | 2011 |
| Manndecorations Limited | Construction | 1998 |
| Manor Gardens II Limited | Construction | 2021 |
| Manor Hill House Limited | Hospitality | 2022 |
| Manorbier Ltd | Administrative & support | 2018 |
| Manorgreen Limited | Households | 1985 |
| Mansell Technology Services Ltd | Information & communication | 2014 |
| Many & Co International Limited | Hospitality | 2019 |
| MAP Chicken Ltd | Hospitality | 2025 |
| MAP Finance Solutions Limited | Professional & scientific | 2022 |
| MAP Group Holdings Limited | Professional & scientific | 2023 |
| MAP Properties 2024 Limited | Real estate | 2024 |
| Maple (225) Limited | Households | 2004 |
| Maple (226) Limited | Households | 2004 |
| Maple Leaf Holidays Limited | Hospitality | 2022 |
| Maple Rock Carpentry Limited | Manufacturing | 2021 |
| Mapleoak Contracts Limited | Construction | 2016 |
| Maramatanga Limited | Arts & recreation | 2022 |
| Marbro Contracts Limited | Construction | 2007 |
| Marcelmonique Pictures Limited | Arts & recreation | 2025 |
| Marchant Schmidt Europe Limited | Manufacturing | 2012 |
| Marches Bottling and Packaging Limited | Manufacturing | 2016 |
| Maric Combined Solutions Limited | Administrative & support | 2014 |
| Marii Media Ltd | Wholesale & retail | 2025 |
| Marine Wenlock Limited | Extraterritorial | 2021 |
| Marinet Limited | Agriculture & fishing | 2014 |
| Mariposa Community Support Ltd | Health & social care | 2023 |
| Marjaan Industries Ltd | Wholesale & retail | 2021 |
| Mark J Electrical Ltd | Construction | 2013 |
| Mark Willott Limited | Information & communication | 2012 |
| MARKESMITH360 Ltd | Professional & scientific | 2022 |
| Markifyer Ltd | Wholesale & retail | 2025 |
| Marksman Leisure Ltd | Arts & recreation | 2011 |
| Marlberrow Properties Limited | Real estate | 2023 |
| Marlbrook (UK) Limited | Professional & scientific | 2000 |
| Marlbrook Holdings Ltd | Financial services | 2025 |
| Marlbrook International Ltd | Administrative & support | 2018 |
| Marlbrook Rise Management Company Limited | Households | 2022 |