| HJB Tech Limited | Information & communication | 2024 |
| HM Estates Limited | Construction | 2006 |
| Hollies Court (Banbury) Management Limited(The) | Real estate | 1983 |
| Holm Engineering Limited | Manufacturing | 2006 |
| Home-Start Southern Oxfordshire | Health & social care | 2005 |
| Homeplan Construction Limited | Construction | 2004 |
| Honeypot Dating Ltd | Other services | 2018 |
| House of Spice (Mill Street) Limited | Hospitality | 2005 |
| Howbery Park Estates Limited | Professional & scientific | 1994 |
| HQQ Restaurant Oxford Ltd | Hospitality | 2020 |
| HR Source Limited | Administrative & support | 2002 |
| HR Wallingford Group Limited | Professional & scientific | 1982 |
| Human Resources Business Partner Ltd | Administrative & support | 2023 |
| Hunayesh Limited | Health & social care | 2007 |
| Huntercombe Golf Club Limited | Arts & recreation | 1963 |
| Huntercombe Golf Shop Limited | Wholesale & retail | 2006 |
| Hyperthetical Limited | Professional & scientific | 2003 |
| Hyvve Kind Limited | Professional & scientific | 2020 |
| I.T. Help and Support Centre Limited | Information & communication | 2005 |
| IAN Murphy Limited | Construction | 2006 |
| Ideas Network 2030 Limited | Other services | 2020 |
| Ilze Elite Barbers Ltd | Other services | 2025 |
| Imotya Ltd | Information & communication | 2003 |
| Impossible Productions Limited | Arts & recreation | 2015 |
| IN Showjumpers Limited | Agriculture & fishing | 2010 |
| Indigo RYE Two Limited | Other services | 2004 |
| Infinity Alignment Ltd. | Health & social care | 2013 |
| Innova Technology Limited | Information & communication | 2003 |
| Innovative Spaces Limited | Wholesale & retail | 2005 |
| Integrate CPD Limited | Education | 2003 |
| Intelligent Counting Limited | Administrative & support | 1996 |
| Inter Church Productions Limited | Arts & recreation | 2000 |
| Interfood Limited | Professional & scientific | 2008 |
| Interfood Slicing Limited | Professional & scientific | 2007 |
| Interfood Systems Limited | Professional & scientific | 2007 |
| Interfood Technology Ltd. | Wholesale & retail | 1999 |
| International Association of Hydrological Sciences Limited | Information & communication | 1992 |
| International Travel Works Ltd | Administrative & support | 2022 |
| Interspares Motorsport Limited | Wholesale & retail | 2003 |
| Intralinks Language and Business Services Limited | Administrative & support | 1994 |
| Inventions Network Limited | Professional & scientific | 1993 |
| IP Asset Holdings Limited | Professional & scientific | 2005 |
| Iron Compass Consultancy Limited | Professional & scientific | 2023 |
| Irons Geophysical Consulting Limited | Mining & quarrying | 2005 |
| Isabella International Camping Limited | Wholesale & retail | 1970 |
| Isherwood-Moss Limited | Real estate | 1960 |
| Isis Accountancy Services Limited | Professional & scientific | 2007 |
| Isis Creative Framing Limited | Manufacturing | 2000 |
| Isis Fluid Control Limited | Wholesale & retail | 1991 |
| Island Women Ltd | Arts & recreation | 2024 |
| Ivan Staines Limited | Administrative & support | 2003 |
| J Dhanjal Transport Limited | Transport & logistics | 2000 |
| J.A. PYE (Oxford) Holdings Limited | Construction | 1977 |
| J.A. PYE (Oxford) Homes Limited | Construction | 1973 |
| J.C. Watts & SON Limited | Agriculture & fishing | 1962 |
| J.F. Horton & Sons (Electrical Contractors) Limited | Construction | 1995 |
| J.M.W. Design Consultancy Limited | Professional & scientific | 1993 |
| J.P. Quinn Limited | Construction | 1999 |
| J.P.H. Electrical Limited | Construction | 2004 |
| Jabez Technology Limited | Manufacturing | 2004 |
| Jade Manufacturing Limited | Manufacturing | 2003 |
| Jansel 2 Management Limited | Real estate | 2016 |
| JC Meadowsweet Ltd | Real estate | 2021 |
| JD Technical Limited | Professional & scientific | 1998 |
| Jemmett Software Development Limited | Information & communication | 2004 |
| John Marks & Khuja LLP | | 2012 |
| Johnsons Bathrooms Limited | Construction | 2008 |
| Jojo's Vineyard Ltd | Agriculture & fishing | 2006 |
| JON Nicholas Golf School Limited | Arts & recreation | 1995 |
| Jordan Slade Limited | Professional & scientific | 2004 |
| JSG Plant Hire & Civil Engineering Limited | Administrative & support | 2006 |
| Juice Hospitality Limited | Administrative & support | 2013 |
| Julia Holberry Associates Limited | Professional & scientific | 2006 |
| K & C. Electrical Services Limited | Construction | 2007 |
| K V a (Consultants) Limited | Real estate | 1984 |
| Kahootz Limited | Information & communication | 2001 |
| Karen Earp Consulting Limited | Professional & scientific | 2021 |
| Kaspar Studio Ltd | Manufacturing | 2021 |
| Kayam Limited | Extraterritorial | 2008 |
| Keepyear Residents Management Limited | Real estate | 2000 |
| Kel-Berg Finance Limited | Wholesale & retail | 1999 |
| Kelhull Limited | Real estate | 1997 |
| Kevin Tinson Limited | Agriculture & fishing | 2003 |
| Key Light Customs Ltd | Wholesale & retail | 2024 |
| Keymax Holdings Limited | Real estate | 2020 |
| Kingsbury Racing Shop Limited | Manufacturing | 2008 |
| Kirtlington Holdings Limited | Extraterritorial | 1886 |
| Kitford Limited | Administrative & support | 2025 |
| Knights Jewellery Limited | Wholesale & retail | 2013 |
| Knox Estates Limited | Administrative & support | 2008 |
| Kolam Partnership Ltd | Arts & recreation | 2002 |
| Kriko Controls Ltd | Manufacturing | 2003 |
| KS Hoses Limited | Other services | 2001 |
| Kubota (U.K.) Limited | Wholesale & retail | 1977 |
| Kutz of Marlow Limited | Other services | 2006 |
| L & H Building Services Limited | Construction | 2004 |
| L C Hughes Limited | Professional & scientific | 2002 |
| L.E.C. Construction Limited | Wholesale & retail | 2006 |
| LA Medusa Ltd | Other services | 2005 |
| Lakewood Management Services Limited | Administrative & support | 2002 |