| Incharge Ltd | Professional & scientific | 2003 |
| Increment Limited | Information & communication | 2001 |
| Indesit Company UK Holdings Limited | Financial services | 2002 |
| Inivis Limited | Information & communication | 2002 |
| Insoft Innovations UK Ltd | Information & communication | 2026 |
| Instrata Ltd. | Information & communication | 2001 |
| INTEREST2INVEST Ltd | Real estate | 2023 |
| Intrarow Limited | Administrative & support | 2023 |
| Ishaara Limited | Information & communication | 2014 |
| ISS Servisystem Limited | Extraterritorial | 1961 |
| J & E Carpentry Contractors Limited | Construction | 2007 |
| J D Consultancy Services Ltd | Professional & scientific | 2002 |
| J&C Consulting Ltd | Professional & scientific | 2018 |
| J&J Sons Ltd | Wholesale & retail | 2025 |
| Jades Beauty Ltd | Other services | 2022 |
| Jaei Consultancy Ltd | Administrative & support | 2023 |
| JAM Tomorrow Investments Ltd. | Real estate | 2001 |
| James a Mackellar Limited | Information & communication | 2005 |
| James Howarth & Co. Limited | Real estate | 2001 |
| JAN Vince Nail Spa Ltd | Other services | 2021 |
| Jason International Engineering Limited | Professional & scientific | 1994 |
| Jefford Carpets Limited | Wholesale & retail | 2002 |
| Jerk UP Ltd | Hospitality | 2019 |
| Jetstream Aviation Limited | Professional & scientific | 1998 |
| JEX Plant Hire Limited | Extraterritorial | 1998 |
| JIM Mandley Limited | Other services | 2005 |
| Jivrat Associates Limited | Hospitality | 1985 |
| Joanne Seaton Limited | Other services | 2007 |
| Jobtheme Limited | Construction | 1988 |
| Joeco Limited | Manufacturing | 2007 |
| John Corfield (Peterborough) Limited | Real estate | 1955 |
| Johnston Agriculture Limited | Administrative & support | 2005 |
| Jolliffe Daking LLP | | 2007 |
| K a Barrett Electrical Limited | Professional & scientific | 2003 |
| K. & J. Carpenter & SON Limited | Construction | 1986 |
| K.M.R. Developments Limited | Construction | 2000 |
| Karen Johnston Counselling Limited | Health & social care | 2004 |
| Katerina Fashions Limited | Wholesale & retail | 1982 |
| KAW Limited | Information & communication | 2009 |
| Kett Autopaints (Anglia) Limited | Wholesale & retail | 2006 |
| Khalstan Field Works Limited | | 2000 |
| Kirsty`S Counting Services Ltd | Professional & scientific | 2007 |
| KKR Software Ltd | Information & communication | 2004 |
| Koma Consulting Limited | Professional & scientific | 2015 |
| Kore Technology Limited | Manufacturing | 1991 |
| Kram Consulting Ltd | Information & communication | 2025 |
| L and S Keshwara Limited | Wholesale & retail | 2001 |
| L D S Cambridge Limited | Professional & scientific | 2007 |
| L&B Walmsley Property Ltd | Real estate | 2025 |
| Lamb Weston UK Ltd | Administrative & support | 1991 |
| Largence Ltd | Information & communication | 2025 |
| Lawrence Smith Joinery Limited | Manufacturing | 2003 |
| LDA 2014 LLP | | 2004 |
| Lemonfield Communications Limited | Professional & scientific | 1997 |
| Lester Pryke Limited | Manufacturing | 2005 |
| LGR Study Abroad Limited | Administrative & support | 2017 |
| Lime Assets Limited | Real estate | 2023 |
| LJ Duffy Ltd | Financial services | 2021 |
| Lockwood Commercial Limited | Real estate | 1996 |
| Lodge Lake Investments Ltd | Real estate | 2006 |
| Longstowe Hall Estate | | 1990 |
| Loqusbeta Limited | Professional & scientific | 2024 |
| Loqustx Limited | Professional & scientific | 2024 |
| Love Farm Ltd | Hospitality | 2025 |
| M & L Ceilings (Cambridge) Ltd | Wholesale & retail | 2003 |
| M & L Sheet Metal Limited | Wholesale & retail | 1996 |
| M Edgley Plumbing & Heating Limited | Construction | 2003 |
| M J Site Services Limited | Construction | 2007 |
| M. Turner Vehicle Repairs Limited | Wholesale & retail | 2005 |
| Maccaruna Limited | Hospitality | 2020 |
| Magnum Tyres Limited | Wholesale & retail | 2003 |
| Maha UK Limited | Manufacturing | 1997 |
| Mallam Dendo Limited | Administrative & support | 2003 |
| Mallory Design Consultants Limited | Administrative & support | 2010 |
| Mandela Street Studios Limited | Real estate | 1986 |
| Mandrel Systems Limited | Information & communication | 1999 |
| Manor Hotel (Alconbury) Limited | Hospitality | 2006 |
| March Town United Football Club Limited | Arts & recreation | 1949 |
| Markiteam Limited | Information & communication | 2002 |
| Martin Wilde Associates Limited | Professional & scientific | 2006 |
| Matrix Resources Limited | Construction | 2003 |
| Maxbyte Limited | Information & communication | 2007 |
| Maya International Limited | Professional & scientific | 2006 |
| Meea Holdings Limited | Financial services | 2021 |
| Meridian Audio Limited | Manufacturing | 1992 |
| Meroncroft Limited | Real estate | 1991 |
| Mgoc Spares Limited | Wholesale & retail | 1985 |
| Michael Wicks Garage Limited | Wholesale & retail | 2002 |
| Michell Instruments Limited | Manufacturing | 1974 |
| Mill House Bloodstock Services Limited | Professional & scientific | 1992 |
| Millennium College UK Limited | Education | 2000 |
| Milne Consulting Limited | Professional & scientific | 2005 |
| Minari International Limited | Information & communication | 1993 |
| Mindfulness Works Limited | Professional & scientific | 2006 |
| Mission Compleat Limited | Manufacturing | 2002 |
| Mnatzaganian Fine Bows Limited | Manufacturing | 2002 |
| Modern Indian Foods Ltd | Hospitality | 2017 |
| Monetarx Ltd | Information & communication | 2025 |
| Morton and Hall Consulting Limited | Professional & scientific | 2005 |
| Morton Consulting Engineers Limited | Professional & scientific | 1991 |