| Moores Farm Estate Management Company Limited | Other services | 2016 |
| Moorfield Road Management Limited | Households | 2013 |
| Moorland Gate Limited | Professional & scientific | 2008 |
| Moose Productions | | 1998 |
| Moqi Travel Ltd | Administrative & support | 2024 |
| Moral Kingdom Limited | Wholesale & retail | 2022 |
| Moral WIN International Limited | Manufacturing | 2019 |
| Morchella Medical Limited | Professional & scientific | 2026 |
| Mordenholt Management Company Limited | Households | 1982 |
| More CHOC0LATE Limited | Wholesale & retail | 2025 |
| Morecock Investments Limited | Real estate | 2013 |
| Morello Quarter Basildon (UK) Ltd | Real estate | 2022 |
| Morgan Heavy Industry Ltd | Professional & scientific | 2022 |
| Morgan Pools Limited | Construction | 2011 |
| Morgan Studios Limited | Professional & scientific | 2005 |
| Morgine Ltd | Financial services | 2018 |
| Morhomes PLC | Financial services | 2017 |
| Mori Architecture Ltd | Professional & scientific | 2025 |
| Morley Brothers (Holdings) Limited | Administrative & support | 2019 |
| Morley Brothers Limited | Other services | 1994 |
| Morning Star Business Consultants Limited | Information & communication | 2017 |
| Morningstar Properties Ltd | Real estate | 2021 |
| Mornington Medical Ltd | Health & social care | 2015 |
| Morphokinetics Ltd | Professional & scientific | 2026 |
| Morris and Bowling Ltd | Other services | 2015 |
| Morris and Graham Ltd | Construction | 2021 |
| Morris and Sons Ltd | Construction | 2000 |
| Morris Investments (Cambridge) Ltd. | Real estate | 2016 |
| Morrow Consultants Limited | Professional & scientific | 2024 |
| Morrow Electronics Limited | Professional & scientific | 1996 |
| Mortgage Solutions Centre Ltd | Financial services | 2006 |
| Mortimer Secretaries Ltd. | Households | 1996 |
| Mortlock Avenue (Management Company) Limited | Professional & scientific | 2005 |
| Mosaic Lives Limited | Professional & scientific | 2014 |
| Mosaic Robotics Ltd | Information & communication | 2025 |
| Mosaic Slough (UK) Ltd | Real estate | 2022 |
| Mosak Group Limited | Manufacturing | 2022 |
| Mosmi Limited | Real estate | 2022 |
| Mossi Properties Ltd | Real estate | 2024 |
| Mostrilla Ltd | Information & communication | 2016 |
| MOT Services (Newmarket) Ltd | Wholesale & retail | 2010 |
| Motas Electronics Limited | Manufacturing | 2017 |
| Mother's Little Helpers Limited | Other services | 2010 |
| Motion Cleaning Machines Ltd | Wholesale & retail | 1998 |
| Motive Marketing Ltd | Professional & scientific | 2021 |
| Motor Mina Ltd | Wholesale & retail | 2022 |
| Motor Vehicle Services (Cambridge) Ltd | Wholesale & retail | 2003 |
| Motus Physiotherapy Ltd | Health & social care | 2022 |
| Moudy Trade Int'L Co., Limited | Manufacturing | 2019 |
| Mount Battenhall Management Company Limited | Households | 2020 |
| Mountain Hare Consulting Ltd | Professional & scientific | 2013 |
| Mountbatten Park Management Company Limited | Households | 2000 |
| Moustakas Service Ltd | Manufacturing | 2024 |
| Move Agile Ltd. | Wholesale & retail | 2025 |
| Move to Cambridge Limited | Administrative & support | 2016 |
| Move Two Limited | Administrative & support | 2009 |
| MOVE2MINGLE CIC | Arts & recreation | 2025 |
| Movebo Ltd | Information & communication | 2013 |
| Movemed Limited | Professional & scientific | 2020 |
| Movexa UK Ltd | Wholesale & retail | 2025 |
| Moviestorm Limited | Information & communication | 2003 |
| Moving Tone Ltd | Arts & recreation | 2004 |
| Moving UP Limited | Education | 2014 |
| Movissima Limited | Information & communication | 2011 |
| Mowbray School of Motoring Limited | Other services | 2011 |
| Mowbray Timber Limited | Wholesale & retail | 2025 |
| Mowell & Co. Limited | Manufacturing | 1972 |
| Mower & Sons Ltd | Administrative & support | 2022 |
| MP Bespoke Projects Ltd | Construction | 2016 |
| MP Painttech Ltd | Manufacturing | 2025 |
| MP75 Composites Ltd | Manufacturing | 2016 |
| MP824 Ltd | Manufacturing | 2024 |
| Mpardal Services Ltd | Manufacturing | 2023 |
| MPB Industries Limited | Manufacturing | 2003 |
| MPG Freshpro Ltd | Hospitality | 2024 |
| MPH Consulting (Cambridge) Ltd | Administrative & support | 2022 |
| MPI Services (Saffron Walden) Limited | Financial services | 2007 |
| MPM Properties (DC) Ltd | Construction | 2024 |
| MPM Properties (EM) Ltd | Construction | 2022 |
| MPM Properties (FY) Ltd | Construction | 2019 |
| MPM Properties (HR) Ltd | Construction | 2024 |
| MPM Properties (OV) Ltd | Construction | 2023 |
| MPM Properties (TH) Ltd | Construction | 2020 |
| MPM Properties Limited | Construction | 1999 |
| MPM Property Holdings (VFS) Ltd | Real estate | 2015 |
| MPN Electrical Contractors Limited | Construction | 2008 |
| Mpofu TM Ltd | Construction | 2025 |
| Mpound Ltd. | Information & communication | 2025 |
| Mprk Properties Limited | Real estate | 2025 |
| MQA Ventures Limited | Professional & scientific | 2015 |
| MR & MRS Smith Limited | Real estate | 2007 |
| MR 8492 Limited Partnership | | 2022 |
| MR AQ London Ltd | Wholesale & retail | 2024 |
| MR Cricket MR Hockey Ltd | Extraterritorial | 2021 |
| MR Hldng Limited | Financial services | 2020 |
| MR J a Hopkinson-Woolley Ltd | Health & social care | 2019 |
| MR Marvel Limited | Arts & recreation | 2002 |
| MR S BET Limited | Arts & recreation | 2024 |
| MR T FRY Heating & Plumbing Ltd | Construction | 2015 |
| MR Taco Takeaway Ltd | Hospitality | 2022 |