| Ciceroni Tours Limited | Administrative & support | 2004 |
| Citadel Policy & Communications Ltd | Administrative & support | 2007 |
| Clacys Limited | Wholesale & retail | 1997 |
| Clarendon Limited | Administrative & support | 2002 |
| Clarke Recruitment Solutions (Staines) Limited | Administrative & support | 2008 |
| Claytons Limited | Hospitality | 1947 |
| Clear & Creative Communications Ltd | Information & communication | 2012 |
| Cleveland Boss Limited | Professional & scientific | 1993 |
| Click and HIT Limited | Wholesale & retail | 2004 |
| Cloche UK Limited | Wholesale & retail | 2003 |
| Club Espresso Ltd | Wholesale & retail | 2024 |
| Clubsports London Ltd | Education | 2014 |
| CMS Estate Planning Ltd | Professional & scientific | 2018 |
| CMS Financial Management Limited | Financial services | 1965 |
| Coburg Components Ltd. | Wholesale & retail | 1981 |
| Cock Horse Service Station Limited | Wholesale & retail | 2007 |
| Cokethorpe Educational Trust Limited | Education | 1963 |
| Colbert Wall Holdings Limited | Professional & scientific | 2015 |
| Collective Intelligence Limited | Professional & scientific | 2000 |
| Collett Brothers (Haulage) Limited | Transport & logistics | 2004 |
| Colliers of Crowmarsh Limited | Wholesale & retail | 2003 |
| Colonial Firearms Limited | Arts & recreation | 1995 |
| Colourburst Lithographic Limited | Professional & scientific | 2000 |
| Communication Support Limited | Professional & scientific | 2004 |
| Company F&Y Ltd | Professional & scientific | 2022 |
| Controlled Reclamation (Oxford) Limited | Other services | 1975 |
| Corn Street Assets Limited | Real estate | 1999 |
| Corn Street Management Company Limited | Households | 1996 |
| Cotefield Ltd | Administrative & support | 2017 |
| Cotswold FOX Clothing Ltd | Wholesale & retail | 2023 |
| Cotswold Vehicle Recovery Limited | Transport & logistics | 2006 |
| Countywide Investments Ltd | Construction | 2013 |
| Courtiers ISA Nominee Limited | Financial services | 2003 |
| Courtiers Nominees Limited | Financial services | 1986 |
| Courtiers PEP Nominee Limited | Financial services | 2003 |
| Courtiers Seid Nominees Limited | Financial services | 2003 |
| Courtiers Support Services Ltd | Financial services | 1995 |
| CP Pools Ltd | Construction | 2015 |
| Cranbrook Construction Limited | Construction | 1998 |
| Creative Evolution Ltd | Administrative & support | 2024 |
| Croft Associates Limited | Manufacturing | 1983 |
| Crown UK Holdings Limited | Professional & scientific | 1996 |
| Crown Windows (Banbury) Limited | | 1982 |
| Cugini Construction Ltd | Construction | 2009 |
| Curzon 2019 Limited | Extraterritorial | 2019 |
| Customer Experience New Product Development Ltd | Information & communication | 2015 |
| CVS Leasing Limited | Financial services | 1997 |
| Cypher Biosciences Ltd | Health & social care | 2025 |
| D & M Plant Hire Limited | Construction | 2000 |
| D M Services (UK) Limited | Construction | 2003 |
| D Morgan Construction Limited | Construction | 2001 |
| D.A. Bowdler (Electrical Contractor) Limited | Construction | 2002 |
| D.W.F. Tulloch & Co. Limited | Agriculture & fishing | 1965 |
| Daci Chauffeurs Ltd | Transport & logistics | 2022 |
| Daily Inks Limited | Wholesale & retail | 2011 |
| Darnoc Limited | Professional & scientific | 2007 |
| Datanet Solutions Limited | Construction | 2005 |
| David Goode Sculpture Limited | Arts & recreation | 1997 |
| David Melling Illustrator Limited | Arts & recreation | 2003 |
| Davison Hardy Plants | | 1978 |
| Delfa Consulting Services Limited | Administrative & support | 2006 |
| Delfa Trading Limited | Wholesale & retail | 2005 |
| Delibo Limited | Hospitality | 2006 |
| Delta-H Technology Ltd | Manufacturing | 2003 |
| Dent Worx (Oxford) Limited | Wholesale & retail | 2003 |
| Dermacademyuk Ltd | Health & social care | 2013 |
| Deruma Limited | Professional & scientific | 2004 |
| Desapro (UK) Limited | Extraterritorial | 2021 |
| Design Difference Limited | Professional & scientific | 2006 |
| Detail Bathrooms Limited | Construction | 2025 |
| DEX Painting Team Limited | Construction | 2024 |
| Dibleys Heritage Limited | Households | 1988 |
| Digitalent (Development) Limited | Manufacturing | 1979 |
| Discerning Journeys Limited | Extraterritorial | 1994 |
| Dmrenting Ltd | Real estate | 2023 |
| Doormarket Ltd | Wholesale & retail | 2025 |
| Doran & Associates (UK) Ltd | Professional & scientific | 2017 |
| Down to Earth Gardens Limited | Extraterritorial | 1996 |
| Dragonfly Consultancy Limited | Professional & scientific | 2020 |
| Durable Developments Limited | Construction | 2005 |
| Dwyer and Sea Gate Limited | Arts & recreation | 2000 |
| E. C. Oxford Limited | Professional & scientific | 2016 |
| Eagle EYE Technologies Limited | Administrative & support | 2018 |
| East Herts Surfacing Limited | Construction | 2025 |
| Eco-Campsites Limited | Hospitality | 2011 |
| Eddolls (Manor Farm) Limited | Agriculture & fishing | 1954 |
| Edicron Limited | Wholesale & retail | 1992 |
| Edwards Precision (Witney) Limited | Extraterritorial | 1999 |
| Eggsact Limited | Arts & recreation | 2000 |
| EHE Ltd | Construction | 2004 |
| Elenalive Healthcare Limited | Health & social care | 2019 |
| Elite Butler Service Ltd | Hospitality | 2019 |
| ELM Mobility Limited | Manufacturing | 2023 |
| Emma Moorby Naturopathy Limited | Health & social care | 2019 |
| Employment Practices Group Ltd | Administrative & support | 2022 |
| EMR Sensitivity Ltd | Health & social care | 2023 |
| Emundi Consulting Limited | Information & communication | 2007 |
| Entee Global Services Limited | Information & communication | 1997 |
| Enviroawards Limited | Professional & scientific | 2020 |
| EPM Projects Limited | Information & communication | 2003 |