| Mirror Image Limited | Other services | 2019 |
| Mitech Consultants Limited | Information & communication | 2000 |
| MJC Services (Cambs) Limited | Administrative & support | 2022 |
| Mjrl Services Ltd | Information & communication | 2018 |
| MJS Controls Limited | Information & communication | 2012 |
| MJS Express Limited | Wholesale & retail | 1998 |
| MJS Sports Coaching Limited | Arts & recreation | 2024 |
| MK Property Investing Ltd | Real estate | 2024 |
| MK Transport Solutions Ltd | Transport & logistics | 2023 |
| MKN Retail Ltd | Wholesale & retail | 2022 |
| Mkpd Limited | Hospitality | 2018 |
| MKR Konsulting Ltd | Information & communication | 2017 |
| MLA Transport Ltd | Transport & logistics | 2024 |
| Mlcnorth Ltd | Hospitality | 2025 |
| MM Coaching Academy Limited | Arts & recreation | 2024 |
| MM Flowers (Plants) Limited | Wholesale & retail | 2025 |
| MM Flowers Limited | Wholesale & retail | 2006 |
| MM Investment Holdings Limited | Wholesale & retail | 2019 |
| MMM Medical Services Ltd | Health & social care | 2025 |
| Mmtrf Investment Group Limited | Real estate | 2018 |
| MNA Garden and Home Improvements Ltd | Extraterritorial | 2023 |
| MND Property Management Ltd | Real estate | 2023 |
| MO Signs Ltd | Professional & scientific | 2020 |
| Mobile Cellular Solutions Limited | Information & communication | 2000 |
| MOBILEPHONEWAREHOUSE6 Limited | Wholesale & retail | 2021 |
| Mobilic Ltd | Wholesale & retail | 2020 |
| Mobility Supermarket (East) Ltd | Wholesale & retail | 2011 |
| Mobility Supermarket Limited | Extraterritorial | 2014 |
| Mobino Limited | Administrative & support | 2017 |
| Model Farm (Fenstanton) Management Company Limited | Households | 2022 |
| Modern World Business Solutions Limited | Professional & scientific | 2025 |
| Modern World Technology Ltd | Information & communication | 2021 |
| Modular Smart Panel Systems Ltd | Construction | 2015 |
| Mofosea Ltd | Wholesale & retail | 2024 |
| Mohamed and Latief Limited | Health & social care | 2007 |
| Moja Cargo Ltd | Transport & logistics | 2014 |
| Molbys Ladies Ltd | Other services | 2026 |
| Molbys Ltd | Other services | 2001 |
| Mole END Commercial Limited | Real estate | 2021 |
| Mole END Consultancy Limited | Professional & scientific | 2019 |
| Monlon Ltd | Households | 2025 |
| Montgomery Communications Limited | Financial services | 2014 |
| Mood With Modesty Ltd | Wholesale & retail | 2021 |
| Moodfield Limited | Administrative & support | 2012 |
| Moogitz Limited | Wholesale & retail | 2017 |
| Moolenaar UK Ltd | Agriculture & fishing | 2014 |
| Moorhouse Drive Residents Association Limited | Real estate | 2007 |
| Mophead Inc Limited | Professional & scientific | 2013 |
| Morgan Leyzan Limited | Wholesale & retail | 2006 |
| Moroccan Journeys Limited | Administrative & support | 2015 |
| Morph Developments J&M Ltd | Construction | 2018 |
| Morrison Gwent Limited | Construction | 1994 |
| Morrison Limited | Professional & scientific | 2003 |
| Mortimer Management Company Limited | Real estate | 1989 |
| Mosaic Pathways Limited | Extraterritorial | 2025 |
| Mother Theresa Care Limited | Health & social care | 2022 |
| Motion to Profit Ltd | Information & communication | 2020 |
| Moto Greg Ltd | Wholesale & retail | 2015 |
| Moto Polonia UK Limited | Arts & recreation | 2026 |
| Motorealm Ltd | Wholesale & retail | 2026 |
| Motoreco Ltd | Wholesale & retail | 2021 |
| Motward Limited | Manufacturing | 1977 |
| Motward Timber Recycling Limited | Water & waste | 1999 |
| Move+Safe Ltd | Transport & logistics | 2013 |
| Movehco Limited | Professional & scientific | 2015 |
| MP9INE Limited | Construction | 2006 |
| MPS Live Ltd | Arts & recreation | 2025 |
| MR H TEK Ltd | Other services | 2023 |
| MR Investments Cambs Ltd | Real estate | 2023 |
| MR Sutton Limited | Construction | 2020 |
| Mr.Dhan Ltd | Transport & logistics | 2025 |
| MRD Property Group Limited | Real estate | 2025 |
| MRI Drylining Ltd | Construction | 2023 |
| MRI Rads Ltd | Health & social care | 2026 |
| MRJ Joinery Ltd | Construction | 2010 |
| MS Johnson Properties Ltd | Financial services | 2017 |
| MT Property Store Limited | Real estate | 2020 |
| Mtiat Retail Limited | Wholesale & retail | 2022 |
| MTL Consult Limited | Professional & scientific | 2021 |
| Muchwood Green Burials Limited | Other services | 2021 |
| Mugo Agency Ltd | Information & communication | 2020 |
| Mukanya Ltd | Health & social care | 2018 |
| Mulberry Tree Gardening Services Ltd | Administrative & support | 2021 |
| Multi-Care Community Services Ltd | Health & social care | 2013 |
| Multiplied Media Ltd | Professional & scientific | 2025 |
| Muncherz DEN Ltd | Hospitality | 2026 |
| Munoz-Elite Flowers Limited | Wholesale & retail | 2011 |
| Music for Little People Limited | Administrative & support | 2003 |
| Music Promotion Limited | Professional & scientific | 1995 |
| Musicstreet Guitars Limited | Wholesale & retail | 2013 |
| Muslim INS | Health & social care | 2016 |
| Must BE Eco Ltd | Manufacturing | 2024 |
| Must BE Sales Ltd | Professional & scientific | 2025 |
| Mutt DEN Ltd | Wholesale & retail | 2025 |
| MVB Studio Limited | Wholesale & retail | 2024 |
| MVP Mortgages Limited | Financial services | 2022 |
| My Careband Ltd | Information & communication | 2026 |
| My Dream Bathroom Ltd | Construction | 2023 |
| My Marketing Portal Ltd | Information & communication | 2025 |
| My Virtual Garden Design Ltd | Administrative & support | 2022 |