| MK Property & Development Ltd | Construction | 2022 |
| Mkay Consulting Ltd | Information & communication | 2023 |
| MKD Initiatives Limited | Real estate | 2018 |
| MKM Consultancy Services Limited | Information & communication | 2022 |
| Mkvk Property Holdings Ltd | Real estate | 2026 |
| ML Motorsport Engineering Ltd | Professional & scientific | 2020 |
| MLE Pyrotechnics Limited | Arts & recreation | 1999 |
| MLG Tailor-Made Travel Ltd | Administrative & support | 2023 |
| MLP Hospitality Limited | Hospitality | 2022 |
| MM Alloy Wheels Repair Ltd | Manufacturing | 2022 |
| MM Carer Ltd | Health & social care | 2025 |
| MM Mobile Ltd | Administrative & support | 2014 |
| MM Pharma Limited | Health & social care | 2005 |
| MM Rares Ltd | Transport & logistics | 2025 |
| MMC Builders Limited | Construction | 2011 |
| MMJ Homes Limited | Real estate | 2024 |
| MMM Holdings Limited | Financial services | 2016 |
| MMN Properties Limited | Construction | 2026 |
| Mnc&C Ltd. | Construction | 2024 |
| Mnence Limited | Professional & scientific | 2023 |
| MNS Flooring Ltd | Construction | 2017 |
| Model Engineers Laser Limited | Wholesale & retail | 2020 |
| Modlitwa Ltd | Arts & recreation | 2025 |
| Moduvie Ltd | Real estate | 2025 |
| Moduvie Property Limited | Real estate | 2026 |
| Mofy AI Ltd | Information & communication | 2025 |
| Mogul’S Consultancy Services Limited | Information & communication | 2019 |
| Mohsin Ltd | Health & social care | 2015 |
| Mojo Fertility Limited | Health & social care | 2022 |
| Moltom Limited | Manufacturing | 2022 |
| Momentous Solutions Limited | Information & communication | 2017 |
| Momentum Recruitment Limited | Administrative & support | 2012 |
| Momiftah ZIA & Co Ltd | Health & social care | 2019 |
| Monarch Carpets Ltd | Wholesale & retail | 2014 |
| Monarch Gateway Ltd | Administrative & support | 2021 |
| Monarch London Ltd | Wholesale & retail | 2024 |
| Monarch Properties | | 1999 |
| Monarch Tax Limited | Professional & scientific | 2014 |
| Monard Precision Engineering Limited | Manufacturing | 1997 |
| Monde DE L'Esthétique Ltd | Wholesale & retail | 2024 |
| Monero Limited | Information & communication | 2025 |
| Monika Cislo Ltd | Wholesale & retail | 2019 |
| Monkeysaurus Ltd | Agriculture & fishing | 2024 |
| Monroh Ltd | Real estate | 2018 |
| Montana Construction Services Limited | Real estate | 2020 |
| Monte Vista Limited | Professional & scientific | 2021 |
| Montello Limited | Information & communication | 2016 |
| Monty Electrical Installations Limited | Construction | 2018 |
| Moon HUT Limited | Health & social care | 2024 |
| Moon Under the Stars Limited | Hospitality | 2019 |
| Moonlight Solutions Ltd | Transport & logistics | 2024 |
| Moore Clearance Ltd | Water & waste | 2022 |
| Moore Property Lettings Ltd | Real estate | 2020 |
| Mops Hair Design Limited | Other services | 2010 |
| Moran Asset Management Limited | Other services | 2006 |
| Moreland Properties Limited | Real estate | 2001 |
| Moreton Acquisitions Limited | Professional & scientific | 2014 |
| Moreton Manor House Limited | Real estate | 2021 |
| Moreton Paddox Management Company Limited | Households | 2005 |
| Morgan Hodgson Consulting Limited | Professional & scientific | 1992 |
| Moriarty Catering Installations Limited | Hospitality | 2007 |
| Moris Express Ltd | Transport & logistics | 2022 |
| Morjaria & Sons Ltd | Real estate | 2022 |
| Morphic Void Limited | Information & communication | 2015 |
| Morrice Holdings Limited | Financial services | 2018 |
| Morris Advisory Group Limited | Financial services | 2025 |
| Morris Logistics Limited | Transport & logistics | 2023 |
| Morrison Assoc Limited | Administrative & support | 2024 |
| Morse Watchmans (UK) Limited | Other services | 1989 |
| Morso UK Limited | Wholesale & retail | 2005 |
| Morten Properties Ltd | Real estate | 2020 |
| Morton Court (Rugby) Limited | Households | 1961 |
| Morton's Engineering Limited | Professional & scientific | 2023 |
| Moscomms Limited | Professional & scientific | 2021 |
| MOT (Test Management) Ltd | Extraterritorial | 2013 |
| Mother India Bilton Limited | Hospitality | 2024 |
| Motolarie Official Ltd | Health & social care | 2019 |
| Motor & Generator Personnel Limited | Manufacturing | 2002 |
| Motor Vehicle Spares Limited | Wholesale & retail | 2021 |
| Motorcycling Great Britain Limited | Professional & scientific | 1998 |
| Motorecruit Limited | Wholesale & retail | 2020 |
| Motors GT Limited | Transport & logistics | 2017 |
| Mount Gardens Residents' Association Limited | Households | 1978 |
| Mourne Enterprises Limited | Professional & scientific | 2011 |
| Movex Industrial Innovations (UK) Limited | Manufacturing | 2012 |
| Mp&Gb Ltd | Real estate | 2024 |
| MPD Transport Ltd | Transport & logistics | 2023 |
| MPG Express UK Limited | Transport & logistics | 2025 |
| MR Express Accounting Ltd | Professional & scientific | 2018 |
| MR M Carpenter Limited | Construction | 2021 |
| MR Robot Ltd | Extraterritorial | 2025 |
| MR Underfloor Limited | Construction | 2022 |
| Mr.Tweety Limited | Administrative & support | 2011 |
| MRB Maintenance Services Limited | Construction | 2013 |
| MRC Commercial Management Ltd | Administrative & support | 2012 |
| MRM European Logistics Ltd | Transport & logistics | 2014 |
| MRS Longevity Ltd | Health & social care | 2026 |
| Mrudula BT Solutions Ltd | Information & communication | 2026 |
| MS HAM Ltd | Other services | 2020 |
| MS HR Ltd | Other services | 2020 |