| Chalgrove Wines Limited | Wholesale & retail | 2010 |
| Chambers Judd Limited | Professional & scientific | 2010 |
| Champion Brickwork Limited | Construction | 2018 |
| Charlett Roofing Services Ltd | Construction | 2018 |
| Charlotte Mews (Bude) Management Company Limited | Households | 2006 |
| Chartram Export Services Limited | Transport & logistics | 2011 |
| CHC Flats Limited | Households | 1992 |
| Chef Publishing Group Ltd | Information & communication | 2023 |
| Chef Publishing Limited | Information & communication | 2017 |
| Chemical Biology Ventures Limited | Administrative & support | 2012 |
| Chesterton Commercial (Hanover 2) Limited | Real estate | 2017 |
| Chevron (Winchester) Limited | Construction | 2015 |
| Chiltern Cataract and Glaucoma Service Ltd | Health & social care | 2016 |
| Chiltern Fine Arts Limited | Wholesale & retail | 2025 |
| Chiltern House Capital Limited | Information & communication | 2024 |
| Chiltern Osteopathic Practice Ltd | Health & social care | 2003 |
| Chinnor Rugby Community Ltd | Education | 2019 |
| Chinnor Rugby Football Club Ltd | Arts & recreation | 2011 |
| CHK Property Limited | Real estate | 2024 |
| Chore Studio Ltd | Information & communication | 2023 |
| Churchill Auctions Limited | Wholesale & retail | 2018 |
| Churchill Property Group (Cornwall) Limited | Real estate | 2004 |
| Cityops Ltd | Information & communication | 2025 |
| CJ Consultancy Solutions Ltd | Administrative & support | 2019 |
| CJH Services Ltd | Information & communication | 2022 |
| CJW Consultancy Limited | Public administration | 2023 |
| Claire Berthet & Partners Ltd | Professional & scientific | 2021 |
| Claire Holmes Consulting Limited | Professional & scientific | 2020 |
| Clean Water Solutions Ltd | Professional & scientific | 2022 |
| Cleaning With a Smile Ltd | Administrative & support | 2020 |
| Clear Sound Ltd | Information & communication | 2018 |
| Clear View Imaging Holdings Limited | Financial services | 2021 |
| Clear View Imaging Limited | Wholesale & retail | 2008 |
| Clearwater Enterprises Ltd | Administrative & support | 2008 |
| Clemor Produce Limited | Wholesale & retail | 2025 |
| Clever Products Limited | Administrative & support | 2002 |
| Clive Musgrove Services Ltd | Information & communication | 2025 |
| Clive Tyrer Ltd | Professional & scientific | 2021 |
| Cloudnine Creative Furnishings Limited | Construction | 2019 |
| Cloudnine Creative Interiors Ltd | Construction | 2012 |
| Cloudnine Logistics Limited | Professional & scientific | 2024 |
| CML Consultants Ltd | Professional & scientific | 2018 |
| Cnightingale Ltd | Health & social care | 2019 |
| Codesco Ltd | Information & communication | 1995 |
| Cognition Energy Ltd | Professional & scientific | 2018 |
| Colehayes Consulting Ltd | Public administration | 2019 |
| Collender Walton Landscaping Ltd | Administrative & support | 2026 |
| Collinsgroundworks & Construction Ltd | Construction | 2015 |
| Colombs Estate Agents Limited | Real estate | 2021 |
| Commersure Services Ltd | Professional & scientific | 2025 |
| Compass Training Academy Ltd | Education | 2024 |
| Completely Care Recruitment Consultants Limited | Other services | 2004 |
| Completely DBS Ltd | Health & social care | 2007 |
| Compound EYE Ltd | Information & communication | 2011 |
| Concentric Capital Limited | Education | 2022 |
| Concept Flooring Services Limited | Construction | 2015 |
| Concept Flooring Technology Limited | Construction | 2000 |
| Concust Limited | Information & communication | 2019 |
| Configrd I.T. Ltd | Information & communication | 2019 |
| Configrd Ltd | Information & communication | 2018 |
| Connect Scaffolding Services Limited | Construction | 2015 |
| Connected Zebra Ltd | Professional & scientific | 2026 |
| Console Hire Ltd | Administrative & support | 2021 |
| Constellation Collective Representation Ltd | Administrative & support | 2025 |
| Continental Cellulose UK Limited | Wholesale & retail | 1988 |
| Contour Leisure Limited | Wholesale & retail | 2011 |
| Contour Precision Limited | Administrative & support | 2009 |
| Cookes Framing Limited | Other services | 2021 |
| Coop Troop Ltd | Wholesale & retail | 2022 |
| Coppock Holdings Ltd | Professional & scientific | 2023 |
| Cora Group Limited | Arts & recreation | 2017 |
| Core Internet Limited | Information & communication | 2025 |
| Cornerstone Oxford Ltd | Professional & scientific | 2014 |
| Corona Supplies Ltd | Manufacturing | 2005 |
| Corporate Finance Group Limited | Financial services | 1986 |
| Corporate Finance Leasing Limited | Financial services | 1983 |
| Corporate Finance Limited | Financial services | 1985 |
| Cotmore Property Limited | Real estate | 2021 |
| Cotswold Clinical Training Limited | Public administration | 2024 |
| Countercurrent Communications Ltd | Professional & scientific | 2014 |
| Countinglab Ltd | Information & communication | 2010 |
| COX the Saddler Limited | Wholesale & retail | 1981 |
| CP Brickwork Oxfordshire Limited | Construction | 2022 |
| Cpress Management Limited | Professional & scientific | 2014 |
| Cpress One Limited | Manufacturing | 2014 |
| CR Build Ltd | Construction | 2022 |
| Crafts CRM Ltd | Professional & scientific | 2022 |
| Cranetech Construction Solutions Limited | Construction | 2003 |
| Crash Repair Group (Bicester) Ltd | Wholesale & retail | 2023 |
| Create Films Ltd | Information & communication | 2025 |
| Creating Health Ltd | Health & social care | 2013 |
| Creative Technology Studio Ltd | Other services | 2024 |
| Credit and Trading Company Ltd | Financial services | 2007 |
| Crendon Coaching Limited | Professional & scientific | 2015 |
| Crest Motorsport Limited | Wholesale & retail | 2011 |
| CRG Rural Limited | Real estate | 2021 |
| Critical IT Supplies Ltd | Information & communication | 2019 |
| Critical Power Supplies Limited | Construction | 2009 |
| Cronza Ltd | Wholesale & retail | 2025 |
| Cross Mill Services Limited | Other services | 2006 |