| Lynx Marine Service Co., Ltd | Manufacturing | 2025 |
| Lynxvale Limited | Construction | 1989 |
| Lynz (UK) Co., Limited | Wholesale & retail | 2016 |
| Lysander Entertainment Ltd | Information & communication | 2012 |
| Lysander V9312 Limited | Administrative & support | 2024 |
| Lyscicon Limited | Professional & scientific | 2024 |
| LYT Media Ltd | Wholesale & retail | 2026 |
| Lyter Ltd | Information & communication | 2024 |
| Lyzeum Ltd | Professional & scientific | 2019 |
| LZ Global Sourcing Co., Ltd | Wholesale & retail | 2021 |
| Lzakmr Limited | Wholesale & retail | 2025 |
| LZZ Dancewear Ltd | Extraterritorial | 2017 |
| L’Arte Bianca Ltd | Hospitality | 2025 |
| M & C Risk Management Ltd | Information & communication | 2015 |
| M & G Auto Repairs Limited | Wholesale & retail | 2017 |
| M & I Investment Properties Limited | Real estate | 2005 |
| M & J Developments (Cambridge) Limited | Construction | 2013 |
| M & KEI Inter-Bene Ltd. | Hospitality | 2025 |
| M & L Cambridge Limited | Professional & scientific | 2012 |
| M & M Heating (Cambs) Ltd | Construction | 2008 |
| M & M Motorcycles Ltd | Wholesale & retail | 2015 |
| M & T Cleaners Ltd. | Households | 2021 |
| M & T Developments Limited | Real estate | 2005 |
| M & Z Caterers Ltd | Hospitality | 2019 |
| M and H Build Ltd | Manufacturing | 2018 |
| M and M Trading (Cambridge) Limited | Wholesale & retail | 2010 |
| M B Consultants (Cambridge) Limited | Professional & scientific | 2015 |
| M Benns Aviation Services Ltd | Professional & scientific | 2021 |
| M D Tiling Company Ltd | Construction | 2010 |
| M Dunster Holding Co Ltd | Professional & scientific | 2022 |
| M Foreman Veterinary Services Ltd | Professional & scientific | 2025 |
| M G Monk & SON Limited | Construction | 2009 |
| M J Bircham & SON Forestry Contractors Ltd | Agriculture & fishing | 2020 |
| M J Rathbone Ltd | Health & social care | 2021 |
| M J Salmon & SON Limited | Construction | 2005 |
| M J White Developments Limited | Construction | 2019 |
| M J Wright Electrical Ltd | Construction | 2008 |
| M M Developers Limited | Construction | 2002 |
| M Marks Limited | Construction | 2018 |
| M P Property Construction Limited | Real estate | 2021 |
| M Plus Product Development Limited | Administrative & support | 2009 |
| M Ralph Electrical Limited | Construction | 2021 |
| M S Ford Associates Limited | Professional & scientific | 2020 |
| M T Roofing and Scaffolding Limited | Construction | 2013 |
| M T Scaffolding Limited | Extraterritorial | 2013 |
| M Wakeling Chimney Services Limited | Construction | 2026 |
| M&B Trans Ltd | Other services | 2015 |
| M&C Associates Ltd | Professional & scientific | 2023 |
| M&C Cambridge Ltd | Transport & logistics | 2015 |
| M&C Stores Ltd | Wholesale & retail | 2020 |
| M&D Fast Food Ltd | Wholesale & retail | 2021 |
| M&J INV Ltd | Real estate | 2022 |
| M&M IT Consultancy Ltd | Information & communication | 2008 |
| M&M Office Solutions Limited | Real estate | 2015 |
| M&M Taxis Ltd | Transport & logistics | 2025 |
| M&P Discounts Ltd | Wholesale & retail | 2025 |
| M&R Secretarial Services Limited | Professional & scientific | 2004 |
| M&S Airport Transfers Ltd | Transport & logistics | 2025 |
| M&T Superclean Ltd | Administrative & support | 2023 |
| M'S Kitchen Limited | Hospitality | 2014 |
| M-Spective Limited | Professional & scientific | 2019 |
| M-Squared Investments Limited | Financial services | 2012 |
| M.B. Mills Limited | Construction | 2009 |
| M.I.S.R Limited | Other services | 2024 |
| M.L. CNC Machining Solutions Ltd | Manufacturing | 2024 |
| M.L.C.S. Limited | Information & communication | 2004 |
| M.S Carpentry Limited | Construction | 2004 |
| M.S. Johnson Engineering Ltd | Wholesale & retail | 2018 |
| M.Somma and Sons Ltd | Manufacturing | 2026 |
| M.U.C.K Ltd | Wholesale & retail | 2020 |
| M.Velikov Composite Ltd | Manufacturing | 2024 |
| M.W. Amps Ltd | Transport & logistics | 2003 |
| M8TRIX Precision Engineering Limited | Manufacturing | 2005 |
| MA Cambs Properties Limited | Real estate | 2023 |
| MA IT 247 Ltd | Information & communication | 2026 |
| MAA Leisure Limited | Hospitality | 2011 |
| Mabel FOX Ltd | Wholesale & retail | 2019 |
| Mabelquinn | Financial services | 2024 |
| Mabon Fashion Trends Co., Ltd | Manufacturing | 2017 |
| MAC Cambridge Lettings Ltd | Real estate | 2026 |
| MAC Mortgages Ltd | Financial services | 2011 |
| MAC Recruitment Services Ltd | Administrative & support | 2013 |
| MAC UK Technical Services Limited | Administrative & support | 2003 |
| Macarthur Reversions Limited | Real estate | 2007 |
| Macca Family Consultancy Limited | Health & social care | 2023 |
| Maccmurray Limited | Professional & scientific | 2012 |
| Macduff 1959 Ltd | Real estate | 2025 |
| Macfarlane Doyle Associates Limited | Administrative & support | 2023 |
| Machinery Trader Group Co., Ltd | Extraterritorial | 2018 |
| Machlab Limited | Professional & scientific | 2025 |
| Machmetal Ltd | Manufacturing | 2025 |
| Machworks LLP | | 2019 |
| Machworx Ltd | Extraterritorial | 2022 |
| Mack Consultancy Services Ltd | Professional & scientific | 2024 |
| Mack Structures Ltd | Manufacturing | 2010 |
| Mackay 1912 Holdings Ltd | Financial services | 2024 |
| Mackay Environmental (Cambridge) Ltd | Financial services | 2024 |
| Mackay Flower Growers Limited | Agriculture & fishing | 2023 |
| Mackay Trading (Cambridge) Limited | Agriculture & fishing | 2023 |
| Mackays Equine Centre Limited | Agriculture & fishing | 2023 |