| Millennium Security Limited | Administrative & support | 2012 |
| Millennium Software Ltd | Administrative & support | 2016 |
| Millers Market and Antiques Centre Limited | Wholesale & retail | 2025 |
| Millie-Rose Solutions Ltd | Public administration | 2020 |
| Millies Organics Limited | Wholesale & retail | 2022 |
| Millman James Ltd | Information & communication | 2012 |
| Millpond Garden Centre Ltd | Wholesale & retail | 2022 |
| Mills Accounting & Bookkeeping Services Limited | Professional & scientific | 2020 |
| Milton Automotive Ltd | Wholesale & retail | 2019 |
| Milton Drinks Limited | Wholesale & retail | 2025 |
| Milton Keynes Artistic Opportunities Society Ltd | Arts & recreation | 2025 |
| Milton Keynes Geocaching Ltd | Administrative & support | 2024 |
| Milton Keynes Gymnastics Limited | Arts & recreation | 1999 |
| Milton Keynes Motor Company Limited | Wholesale & retail | 2010 |
| Milton Keynes Reprographics Ltd | Manufacturing | 2014 |
| MILTON52 Ltd | Construction | 2024 |
| Mima Creative Ltd | Professional & scientific | 2025 |
| Mimo's Grill Ltd | Hospitality | 2017 |
| Mina Transport Ltd | Transport & logistics | 2022 |
| Mind and Body Fitness Ltd | Professional & scientific | 2024 |
| Mind Your Beans Consulting Limited | Professional & scientific | 2019 |
| Mind Your Beans Limited | Real estate | 2017 |
| Mind, Money and Business Ltd | Professional & scientific | 2017 |
| Minder Limited | Manufacturing | 2007 |
| Mindful Mantra Ltd | Information & communication | 2024 |
| Mindgames Incorporated Limited | Education | 2024 |
| Mindme Ltd | Wholesale & retail | 2020 |
| Mindmetrix Ltd | Information & communication | 2025 |
| Mindpath Consulting Ltd | Health & social care | 2025 |
| Mindr Holdings Ltd | Construction | 2024 |
| Mindr Shared Portfolio Ltd | Real estate | 2024 |
| Mindset Associates LLP | | 2017 |
| Mindsmaking Brands Limited | Information & communication | 2022 |
| Mindstormerz Ltd | Wholesale & retail | 2023 |
| Minerisalt Ltd | Wholesale & retail | 2026 |
| Minerva Medical & Training Ltd | Education | 2026 |
| Mini Miracles Childcare Ltd | Health & social care | 2024 |
| Minigolfco Ltd | Arts & recreation | 2022 |
| Minilan Ltd | Information & communication | 2024 |
| Ministry of Christ Church Ltd | Other services | 2019 |
| Ministry of Crown & Beauty Ltd | Professional & scientific | 2025 |
| Minmoonz Ltd | Information & communication | 2017 |
| Minnis Bay Stores Limited | Wholesale & retail | 2005 |
| Mint Advice Limited | Professional & scientific | 2021 |
| Mint Alloys Limited | Wholesale & retail | 2006 |
| Mint Beverages Limited | Manufacturing | 2023 |
| Mint Construction (Bedford) Limited | Construction | 2013 |
| Mint Ovens Ltd | Administrative & support | 2026 |
| Mint Procurement & Supply Chain Services Ltd | Professional & scientific | 2025 |
| Mira Consult Limited | Other services | 2010 |
| Miracle Church of GOD in Christ | Other services | 2022 |
| Mirador MK Limited | Hospitality | 2025 |
| Mirage AL Noor Ltd | Wholesale & retail | 2026 |
| Mirela Care Ltd | Health & social care | 2018 |
| Mirembe Lane Ltd | Wholesale & retail | 2025 |
| Mirolak Ltd | Wholesale & retail | 2018 |
| Mirt Construction Ltd | Construction | 2024 |
| Mirza Electrical Limited | Manufacturing | 2016 |
| Miscombe Developments (Hartington) Ltd | Construction | 2012 |
| Miso Wing Properties Limited | Real estate | 2024 |
| Missions Division Limited | Education | 2022 |
| Missy Trends Ltd | Wholesale & retail | 2024 |
| Mister Packaging Limited | Extraterritorial | 1989 |
| Mitchell Prockter (Financial Services) Limited | Financial services | 1982 |
| Mitko Kebab Ltd | Hospitality | 2026 |
| MIV Consulting Limited | Administrative & support | 2013 |
| Mivira Limited | Real estate | 2020 |
| Mixi Construction Limited | Construction | 2018 |
| MJ Electrical & Building Services Ltd | Construction | 2015 |
| MJ Murphy Electrical Limited | Construction | 2002 |
| MJ Renewables Ltd | Construction | 2023 |
| MJ SAW & Drill Solutions Limited | Manufacturing | 2013 |
| MJ Smith Interiors Limited | Construction | 2014 |
| Mjad Ltd | Information & communication | 2023 |
| MJC Fleet Ltd | Wholesale & retail | 2024 |
| MJL Cleaning and Garden Ltd | Administrative & support | 2026 |
| MJL Communications Ltd | Information & communication | 2023 |
| MJM Lounge Limited | Hospitality | 2019 |
| MJP Interiors Limited | Construction | 2017 |
| MJR Autos Ltd | Wholesale & retail | 2025 |
| MJS Homes Ltd | Real estate | 2019 |
| MK City Limited | Construction | 2015 |
| MK City Supplies Ltd | Wholesale & retail | 2020 |
| MK Construct Ltd | Transport & logistics | 2021 |
| MK Curry Ltd | Hospitality | 2017 |
| MK Delicacies Limited | Hospitality | 2024 |
| MK Food & Wine Elstow Ltd | Wholesale & retail | 2019 |
| MK Gentlemen's ROW Ltd | Other services | 2022 |
| MK Harko Limited | Hospitality | 2023 |
| MK LET Experts Ltd | Real estate | 2025 |
| MK Plumbing & Electrical Services Ltd | Construction | 2019 |
| MK Pro Basketball Ltd | Arts & recreation | 2020 |
| MK SERVICES-K9 Ltd | Administrative & support | 2024 |
| MK Sports Bar & Lounge Ltd | Hospitality | 2019 |
| MK Synergy Builders Ltd | Construction | 2023 |
| MK Transport Bedford Ltd | Transport & logistics | 2017 |
| MK Transporting Ltd | Transport & logistics | 2026 |
| MK Works Groups Ltd | Information & communication | 2024 |
| Mk-Aerials Ltd | Information & communication | 2024 |
| MK1 Heating Limited | Construction | 2022 |