| Hurseys Limited | Construction | 2004 |
| Hydac International Limited | Professional & scientific | 1991 |
| I M Impy Limited | Manufacturing | 2003 |
| Image Homes and Developments Limited | Construction | 2007 |
| IN Time Studios Limited | Wholesale & retail | 2003 |
| In-Cad Services Ltd | Administrative & support | 2006 |
| Indisys Business Solutions Limited | Professional & scientific | 2003 |
| Infinite Office Products Limited | Wholesale & retail | 2002 |
| Integral I.T. Solutions Ltd | Information & communication | 1996 |
| Intercity Electric & Mechanical Services Limited | Professional & scientific | 1964 |
| International Onepipe Heater Limited | Construction | 1921 |
| Invest in Your Career Limited | Administrative & support | 2006 |
| J H Bettinson Limited | Professional & scientific | 2006 |
| J P Plumbing Limited | Construction | 2017 |
| J. Heebink (Milton Keynes) Limited | Transport & logistics | 1995 |
| J.A.K. Design & Construction Limited | | 1988 |
| J.C. Frost & Co. (Ashford) Ltd | Real estate | 1989 |
| J.C.Frost & Co.(Windsor) Ltd. | Real estate | 1989 |
| J.D. Ware Limited | | 1949 |
| J.S.Smith(High Wycombe)Limited | Professional & scientific | 1946 |
| Jacarem Limited | Wholesale & retail | 1987 |
| James Booth Aluminium Limited | | 1959 |
| James Ross Consulting International Limited | Administrative & support | 2005 |
| James Walk Management Company Limited | Households | 2019 |
| Jasline Limited | Financial services | 1993 |
| Jbrg Investment Limited | Financial services | 2023 |
| Jetta Consultants Limited | Information & communication | 2001 |
| Jkps Properties (P) Ltd | Real estate | 2023 |
| JRS (Bucks) Ltd | Hospitality | 2025 |
| Kasearma Limited | Health & social care | 2019 |
| KBA Solutions Limited | Professional & scientific | 2003 |
| Kehr Management Ltd | Construction | 2007 |
| Kina Business Services Limited | Professional & scientific | 2005 |
| Kiwi UK Properties Ltd | Real estate | 2021 |
| Knight Surprise Ltd | Other services | 2004 |
| Kossway Automatics Limited | Administrative & support | 1963 |
| Kris Valeting Ltd | Wholesale & retail | 2014 |
| Lancasters (Holdings) Limited | Professional & scientific | 2011 |
| Lancefield Consulting Limited | Professional & scientific | 2005 |
| Langley Nursing Home Limited | Health & social care | 1992 |
| Latimer Consulting Limited | Information & communication | 1991 |
| Lewis Carol Construction Limited | | 1988 |
| Lifestyle Infrastructure Limited | Real estate | 2023 |
| Limrah Merchant Services Ltd | Financial services | 2015 |
| Lindsay Timber Company Limited | Professional & scientific | 1942 |
| Little Company (Stationers) Limited(The) | | 1987 |
| Living Props Limited | Other services | 1991 |
| LNG2020 Limited | Professional & scientific | 2007 |
| Locke & Soares Limited | | 1938 |
| Lorimpex UK Limited | Wholesale & retail | 2002 |
| Lowndes Construcion Limited | | 1970 |
| Lucas Flett Holdings Ltd. | Manufacturing | 1992 |
| Lucky Dog Inc. Ltd | Information & communication | 2007 |
| Lycom Limited | Agriculture & fishing | 2006 |
| M. R. S. Transfers Limited | Manufacturing | 2006 |
| Macfax Limited | | 1985 |
| Madacovi Ltd | Information & communication | 2006 |
| Maltman's Green School Trust Limited | Education | 1967 |
| Marbleweb Limited | Professional & scientific | 2006 |
| Marchard Limited | Professional & scientific | 2005 |
| MBS Medical Limited | Health & social care | 2007 |
| Meaujo (727) Limited | Agriculture & fishing | 2006 |
| Medical Creatives Holdco Ltd | Financial services | 2026 |
| Mercy Medical Services Ltd | Professional & scientific | 2004 |
| Metropolitan Personal Security Services Limited | Arts & recreation | 1987 |
| Mid-Sussex Property Co. Limited | Wholesale & retail | 1986 |
| Middlesex Design Ltd | Construction | 2026 |
| Minerva Mezzanines Limited | | 1982 |
| MJF Ductwork Ltd | Construction | 2007 |
| Moat House RTE Company Limited | Administrative & support | 2005 |
| Moreshore Limited | | 1986 |
| MS7 Real Estates Holdings LLP | | 2019 |
| My Body Temple Limited | Health & social care | 2011 |
| N Allford Motors Ltd | Wholesale & retail | 2003 |
| Najah Capital Limited | Real estate | 2005 |
| Nashtal and Company Limited | Manufacturing | 1948 |
| Nearsword Limited | Information & communication | 1983 |
| Newsmedia Limited | | 1987 |
| Non-Sag Seating Company Limited | Manufacturing | 1948 |
| North South Investments (UK) Limited | Real estate | 2005 |
| Norwood Technical Services Ltd | Wholesale & retail | 2003 |
| Notec Engineers Limited | | 1977 |
| Nova Fundraising & Associates Ltd | Professional & scientific | 2022 |
| Nuvanta Consultancy Limited | Professional & scientific | 2025 |
| Nylon Colours (Holdings) Limited | Professional & scientific | 1990 |
| O&A Solutions Ltd | Professional & scientific | 2016 |
| OIL and GAS Consulting Ltd | Professional & scientific | 2022 |
| Oled Consultancy Limited | Information & communication | 2004 |
| OM Ambica Limited | Wholesale & retail | 2007 |
| One Salon Hairdressing Ltd | Other services | 2003 |
| OPEN4YOU Ltd | Real estate | 2013 |
| Optimate Limited | Information & communication | 1987 |
| Osborne Systems Limited | Professional & scientific | 2005 |
| P.M. Films Limited | | 1978 |
| P.R. Greenough Construction Limited | Wholesale & retail | 1986 |
| PAK-8 Distributors Limited | | 1979 |
| Pandect Instrument Laboratories Limited | Manufacturing | 1954 |
| Parents AS First Teachers UK Limited | Education | 2006 |
| Paul Inns Haulage Limited | Transport & logistics | 2000 |
| Payroll Management Limited | Administrative & support | 1992 |