| Mamas Help Ltd | Wholesale & retail | 2026 |
| Manchester Loans and Securities Ltd | Financial services | 2008 |
| Manhattan MK Ltd | Extraterritorial | 2015 |
| Manor Farm Dwellings Limited | Real estate | 2004 |
| Mansion House Investments Limited | Real estate | 2002 |
| Mappa Mundi Surveys Limited | Professional & scientific | 2012 |
| Maria's Handcraft Studio Ltd | Manufacturing | 2026 |
| Marion Ellis Limited | Professional & scientific | 2018 |
| Marriott International Group Ltd | Administrative & support | 2020 |
| Martingale Pet Products Ltd. | Wholesale & retail | 2020 |
| Mash IT UP Limited | Arts & recreation | 2014 |
| Mason Valuation Consultants Limited | Professional & scientific | 2025 |
| Matrix Interim Logistics Ltd | Professional & scientific | 2018 |
| Matt Wilkinson General Builders Limited | Construction | 2020 |
| Matthews Services Ltd | Administrative & support | 2019 |
| Maverick Capital Holdings Ltd | Real estate | 2025 |
| Maverick Commercial Ltd | Real estate | 2024 |
| Maverick Property Investments Limited | Real estate | 2014 |
| Maverick Residential Ltd | Real estate | 2024 |
| Mavpad Ltd | Administrative & support | 2016 |
| Mazz FIC Ltd | Professional & scientific | 2025 |
| Mazz Holdings Ltd | Financial services | 2021 |
| MBL Associates Limited | Professional & scientific | 2020 |
| MC Flooring (UK) Limited | Construction | 2014 |
| Mccarville & Co. Limited | Professional & scientific | 2024 |
| MCH Property Ltd | Real estate | 2017 |
| MCL Machinery Ltd | Manufacturing | 2026 |
| Mclean's Glass (Oxford) Limited | Construction | 2009 |
| MD Property Investments Limited | Real estate | 2016 |
| Meadow View (Long Buckby) Management Company Limited | Households | 2023 |
| Mechsrmengineering Ltd | Professional & scientific | 2024 |
| Medi-Productions Limited | Professional & scientific | 2008 |
| Meditas Limited | Wholesale & retail | 1992 |
| Medsphere Ltd | Health & social care | 2022 |
| Mehr Group Ltd | Real estate | 2020 |
| Mercers Manor Barns Limited | Real estate | 2003 |
| Meridian Medical Consulting Ltd | Health & social care | 2026 |
| Merkan.Cia Freight Limited | Transport & logistics | 2013 |
| Michael Price Accountancy Limited | Extraterritorial | 2015 |
| Michael Price Associates Ltd | Professional & scientific | 2007 |
| Michael Roberts Solutions Ltd | Administrative & support | 2018 |
| Michaelpattinson.Com Ltd | Professional & scientific | 2024 |
| Michal Wezykowski Limited | Information & communication | 2024 |
| Middleton Cleaning Services Ltd | Administrative & support | 2025 |
| Mightdo TOO Ltd | Professional & scientific | 2023 |
| Miihaus Ltd | Professional & scientific | 2018 |
| Mike Hordynski Ltd | Construction | 2012 |
| Milcraft Limited | Manufacturing | 2005 |
| Millburs Stud Ltd | Agriculture & fishing | 2020 |
| Milton & Ward Ltd | Real estate | 2009 |
| Milton Keynes Bathrooms Ltd. | Construction | 2019 |
| Milton Keynes Fencing Limited | Administrative & support | 2003 |
| Milton Keynes Green Businesses Network CIC | Other services | 2026 |
| Milton Keynes Plant Hire Ltd | Administrative & support | 2025 |
| Milton Keynes Podiatry Plus Limited | Health & social care | 2023 |
| Milton Keynes Property Sales Limited | Real estate | 2004 |
| Milton Keynes Scaffolding Specialists Ltd | Construction | 2017 |
| Milton Klee Ltd Ltd | Wholesale & retail | 2025 |
| Milution UK Ltd | Administrative & support | 2026 |
| Minor Disaster Games Ltd | Wholesale & retail | 2024 |
| MINUS71 Limited | Information & communication | 2024 |
| Mirrormeai Ltd | Information & communication | 2025 |
| Miss Saint Limited | Professional & scientific | 2012 |
| Mission Events Ltd | Professional & scientific | 2024 |
| Mjemery Holdings Limited | Financial services | 2022 |
| MJM Truck & Trailer Services Limited | Manufacturing | 2013 |
| MJP Race Prep Limited | Wholesale & retail | 2010 |
| MK Accountancy & Taxation Services Limited | Professional & scientific | 2002 |
| MK Bathrooms Showroom Ltd | Wholesale & retail | 2025 |
| MK Bricklaying & Landscaping Ltd | Construction | 2020 |
| MK City Scaffolding Ltd | Construction | 2022 |
| MK Cleaning FM Ltd | Administrative & support | 2026 |
| MK Express Executive Ltd | Transport & logistics | 2021 |
| MK GAS 24/7 Limited | Construction | 2015 |
| MK GAS Plumbing Heating Ltd | Construction | 2019 |
| MK Munchies Ltd | Hospitality | 2025 |
| MK Plumbing Heating GAS Ltd | Construction | 2025 |
| MK Power Electrical Limited | Professional & scientific | 2015 |
| MK Power Limited | Construction | 2010 |
| MK SAS Transport Group Ltd | Transport & logistics | 2026 |
| MK Spice House Ltd | Hospitality | 2024 |
| MKC Property Ltd | Real estate | 2020 |
| Mkmc Food Business Support Ltd | Hospitality | 2023 |
| Mkone Business Centres Ltd | Real estate | 2008 |
| MM Analytics Limited | Administrative & support | 2010 |
| MNS Saharan Ltd | Real estate | 2023 |
| Mobileart Limited | Arts & recreation | 2026 |
| Modish Nest Ltd | Professional & scientific | 2026 |
| Mohan Services Limited | Health & social care | 2009 |
| Monsa Property Limited | Health & social care | 2021 |
| More Than Just a Game (Mtjag) Ltd | Professional & scientific | 2019 |
| Morgan and Smith Limited | Other services | 2025 |
| Morland Grange (Chantrey) Management Company Limited | Households | 2004 |
| Mossara Limited | Other services | 2024 |
| Motor Test MK Ltd | Wholesale & retail | 2012 |
| Motorway Services Limited | Wholesale & retail | 1959 |
| Mouse Hunters Ltd | Administrative & support | 2013 |
| MPA Group Holdings Employees Trustee's Ltd | Financial services | 2023 |
| MPA Group Holdings Ltd | Financial services | 2023 |
| MPA Group Ltd | Administrative & support | 2019 |