| Crispin Derby Limited | Professional & scientific | 1994 |
| Cristal Health Ltd | Information & communication | 2019 |
| CRM (Oxford) Holdings Limited | Financial services | 2024 |
| CRM Company Services Limited | Professional & scientific | 2000 |
| Crobe Renewables Ltd | Manufacturing | 2025 |
| Crocus Education Ltd | Professional & scientific | 2019 |
| Croft Vehicle Repairs Limited | Wholesale & retail | 2019 |
| Cromwell Solutions Limited | Professional & scientific | 2020 |
| Cron Limited | Information & communication | 2024 |
| Croprime Ltd | Professional & scientific | 2018 |
| Crowley and Crowley Ltd | Professional & scientific | 2011 |
| Crown & Nest Ltd | Real estate | 2025 |
| Crownco Ltd | Wholesale & retail | 2023 |
| Crowne Limited | Information & communication | 2014 |
| Crownhouse Entertainment Ltd | Professional & scientific | 2020 |
| Croydon Wilds Ltd | Professional & scientific | 2023 |
| CRP Services Limited | Wholesale & retail | 2022 |
| Cruxial Ingredients Limited | Manufacturing | 2025 |
| Crypt-Tech Solutions Limited | Information & communication | 2020 |
| Cryptinix Trading Global Ltd | Financial services | 2025 |
| Crypto Index Series Limited | Information & communication | 2019 |
| Crystal Windows (Oxford) Ltd | Administrative & support | 2018 |
| CS Boswell Memorials Ltd | Other services | 2018 |
| CS CMC Consulting Ltd | Professional & scientific | 2023 |
| CS Hexagon Development Limited | Construction | 2024 |
| Cshtech Ltd | Information & communication | 2017 |
| CSM Communications Ltd | Administrative & support | 2012 |
| CT Live Limited | Professional & scientific | 2006 |
| Ctrl ALT DEL Limited | Information & communication | 2020 |
| Cubaneight Limited | Professional & scientific | 2009 |
| Cube 21 Limited | Administrative & support | 2008 |
| Cubing Ideation Limited | Professional & scientific | 2026 |
| Cuckoo Fish Limited | Other services | 2014 |
| Cuddesdon Enterprises Ltd | Hospitality | 2025 |
| Culham Electromagnetics Limited | Professional & scientific | 2007 |
| Culture Elite Education Limited | Education | 2018 |
| Culver Consultants and Investments Ltd | Health & social care | 2021 |
| Cumnor Gardens Residents Management Company Limited | Real estate | 2005 |
| Cumnor Parish News CIC | Information & communication | 2019 |
| Cumnor Trading Limited | Real estate | 2010 |
| Cupec Limited | Manufacturing | 2005 |
| Cura Digital Ltd | Information & communication | 2025 |
| Cura Gate Ltd | Health & social care | 2025 |
| Curavesta Property Holdings Limited | Real estate | 2024 |
| Curiosity Coaching Ltd. | Other services | 2023 |
| Curry Favour Limited | Administrative & support | 2019 |
| Currydor Limited | Hospitality | 2013 |
| Curtains Made Simple Limited | Wholesale & retail | 2008 |
| Curtis Pope Ltd | Professional & scientific | 2024 |
| Curve Graphics Limited | Professional & scientific | 2023 |
| Customer Driven Solutions Limited | Information & communication | 1995 |
| Cutting Edge Diamond Drilling Limited | Construction | 2012 |
| Cuttlefish Software Ltd | Information & communication | 2019 |
| CW Property (Oxford) Ltd | Real estate | 2026 |
| CWC Oxford Ltd. | Wholesale & retail | 2013 |
| CY Research and Development Ltd | Professional & scientific | 2023 |
| Cyanocapture Ltd | Professional & scientific | 2021 |
| Cyanocapture Nominee Limited | Professional & scientific | 2024 |
| Cyber Anarchist Ltd | Financial services | 2023 |
| Cyberlynx Ltd | Wholesale & retail | 2025 |
| Cybersafe International Limited | Information & communication | 2001 |
| Cybersafe Limited | Information & communication | 1996 |
| CYC DU Soleil Community Interest Company | Arts & recreation | 2018 |
| Cyclability CIC | Manufacturing | 2023 |
| Cyclops Limited | Professional & scientific | 2007 |
| Cypher Business Intelligence Limited | Professional & scientific | 2018 |
| Cypher Limited | Professional & scientific | 2019 |
| Cypress Point Ltd | Wholesale & retail | 2025 |
| Cyrenaeus | Health & social care | 2022 |
| Cyril DE Walden Limited | Real estate | 2023 |
| Cyrus Management Limited | Households | 2007 |
| D & M Thermal Limited | Construction | 2024 |
| D 2 B Construction Ltd | Construction | 2009 |
| D 444 Limited | Extraterritorial | 2022 |
| D a Tyrer Lets Limited | Real estate | 2024 |
| D Bryan Electrical Limited | Construction | 2012 |
| D C F Modelling Limited | Other services | 2011 |
| D Carter Plastering Limited | Construction | 2003 |
| D Direct Limited | Wholesale & retail | 2017 |
| D F Williams Cleaning Services Limited | Administrative & support | 1978 |
| D Fainman Holdings Limited | Financial services | 2025 |
| D Imaging Ltd | Health & social care | 2020 |
| D J & M Associates Ltd | Professional & scientific | 2016 |
| D J Y Property Service LLP | | 2026 |
| D Jones Creative Ltd | Information & communication | 2025 |
| D K Creed Limited | Construction | 2026 |
| D K S & SON Services Ltd | Construction | 2007 |
| D Morgan Construction Streetwork Ltd | Construction | 2019 |
| D Morgan Holdings Ltd | Financial services | 2021 |
| D R Barrett Limited | Health & social care | 2015 |
| D S Building Services & Maintenance Ltd | Construction | 2020 |
| D Shepherd and SON Limited | Construction | 2026 |
| D'Arblay Wealth Advisers Ltd | Professional & scientific | 2024 |
| D'Arblay Wealth Limited | Financial services | 2024 |
| D'Arrive Ltd | Transport & logistics | 2021 |
| D. & a. Contracts Limited | Construction | 1972 |
| D.A. Gibbon (Contractors) Limited | Manufacturing | 2012 |
| D.A.Miles & Sons Limited | Construction | 2005 |
| D.E.C. (Oxford) Limited | Construction | 1979 |
| D.G.Accountancy & Taxation Services | | 1993 |