| Clements Lane Management Company Limited | Real estate | 2010 |
| CLI Craft Ltd | Information & communication | 2025 |
| Clickstay Ltd. | Administrative & support | 2013 |
| Cliff Newport Carpentry Ltd | Construction | 2016 |
| Clinical Options Limited | Health & social care | 2014 |
| Clive Catt Consulting Limited | Information & communication | 2022 |
| Clouds Atelier Ltd | Manufacturing | 2018 |
| Clover Stroud Limited | Arts & recreation | 2009 |
| CMK Technology Limited | Administrative & support | 2011 |
| CMM Transport Limited | Transport & logistics | 2018 |
| Cmpi Limited | Real estate | 2015 |
| CMR Intech Limited | Information & communication | 2003 |
| CMT Assistance Ltd | Administrative & support | 2018 |
| Coaching for Executives Limited | Professional & scientific | 2015 |
| Coconut Property Limited | Real estate | 2017 |
| Code-Block Ltd | Information & communication | 2017 |
| Codergy Ltd | Information & communication | 2019 |
| Coffeyford Limited | Health & social care | 2016 |
| Coffox Limited | Professional & scientific | 2006 |
| Coldly Ocean Ltd | Wholesale & retail | 2025 |
| Coleshill Smile Care Limited | Health & social care | 2014 |
| Collectors Merchants Limited | Wholesale & retail | 1995 |
| College Yard Residents Association Limited | Professional & scientific | 1986 |
| Collins (UN) Limited | Information & communication | 2015 |
| Collins Advanced Engineering Limited | Information & communication | 2014 |
| Colonial Spirits Ltd | Wholesale & retail | 2025 |
| Colour Blind Awareness (Consulting) Ltd | Professional & scientific | 2017 |
| Comley & Collier Ltd | Construction | 2023 |
| Command Partners LLP | | 2013 |
| Commercial Mortgages Store Limited | Financial services | 2020 |
| Commonwealth Research Group Ltd | Other services | 2024 |
| Compact Electronics Ltd | Manufacturing | 2016 |
| Complete Building Concepts Limited | Administrative & support | 2008 |
| Complete Connections (Manufacturing) Limited | Information & communication | 2002 |
| Complex Business Solutions Ltd | Administrative & support | 2016 |
| Composite Conclusions Limited | Professional & scientific | 2016 |
| Compound Limited | Real estate | 1992 |
| Computerpro Ltd | Information & communication | 2025 |
| Concertim Limited | Information & communication | 2016 |
| Confident & Connected Ltd | Education | 2020 |
| Confident Smile Services Limited | Professional & scientific | 2022 |
| Coniston Energy Limited | Energy | 2018 |
| Connecting Technologies International Ltd | Information & communication | 2023 |
| Connie's Academy Ltd | Education | 2023 |
| Conrrs Ltd | Education | 2021 |
| Conservation Resources (UK) Limited | Administrative & support | 2006 |
| Consortium Capital Limited | Professional & scientific | 2008 |
| Consortium Finance Limited | Professional & scientific | 2009 |
| Consortium Maritime Capital Ltd | Professional & scientific | 2026 |
| Consortium Maritime Trading Limited | Wholesale & retail | 2013 |
| Consortium Real Estate Partners Ltd | Professional & scientific | 2012 |
| Consortium Yachting Partners Limited | Financial services | 2018 |
| Construction Safety Solutions Limited | Professional & scientific | 2008 |
| Construction Sector Services Limited | Professional & scientific | 2005 |
| Consulting Synergy Ltd | Professional & scientific | 2016 |
| Contractile Limited | Construction | 2023 |
| Cooke Capital Investments Ltd | Real estate | 2024 |
| Coolcarz UK Ltd | Manufacturing | 2014 |
| Cools Developments Limited | Construction | 2026 |
| Coombs Investment Group Limited | Real estate | 2023 |
| Cooper Furniture Limited | Manufacturing | 2006 |
| Cooper Simms Associates Limited | Professional & scientific | 1993 |
| Cooz's Limited | Information & communication | 2009 |
| Coppice Meadow Limited | Agriculture & fishing | 2021 |
| Copse Hollow Limited | Health & social care | 2019 |
| Copthall Flats Management Limited | Households | 1987 |
| Cordrock Development Ltd | Construction | 2019 |
| Corinium Estates Land Development Limited | Construction | 1987 |
| Cornerstone Properties (Thame) Limited | Real estate | 1957 |
| Coroc Ltd | Hospitality | 2020 |
| Cosmetident Limited | Health & social care | 2012 |
| Costviz Ltd | Professional & scientific | 2024 |
| Cosy Life Ltd | Wholesale & retail | 2020 |
| Cotmore Construction Ltd | Construction | 2022 |
| Cotswold Classic Vehicle Hire Ltd | Administrative & support | 2023 |
| Cotswold Heritage Decorators Ltd | Construction | 2025 |
| Cotswold Soft Furnishings Limited | Manufacturing | 2010 |
| Cottisford Farms Limited | Agriculture & fishing | 1997 |
| County Water Limited | Water & waste | 2015 |
| Court Lettings Ltd | Real estate | 2023 |
| Courtivate Ltd | Professional & scientific | 2024 |
| Coveney Associates Consulting Limited | Professional & scientific | 2011 |
| Cowry Ltd | Information & communication | 2018 |
| Coys of London Automobiles Limited | Wholesale & retail | 2020 |
| CP Collective Ltd | Wholesale & retail | 2026 |
| Crafted Construction & Carpentry Ltd | Construction | 2026 |
| Cramart Limited | Hospitality | 2010 |
| Crawford Homes Ltd | Real estate | 2021 |
| Cream Base Ltd | Manufacturing | 2026 |
| Create Engineering Consultancy Ltd | Professional & scientific | 2023 |
| Creating Whole School Wellbeing Ltd | Extraterritorial | 2024 |
| Creative & Artistic Storage Ltd | Arts & recreation | 2025 |
| Creative Modelling Ltd | Professional & scientific | 2011 |
| Credit Marketing Ltd | Professional & scientific | 2014 |
| Creststone Developers Ltd | Construction | 2025 |
| Creststone Investment Ltd | Real estate | 2026 |
| Cridland and Co Limited | Real estate | 2010 |
| Crispin M White Limited | Professional & scientific | 2015 |
| Cristal E Services Ltd | Construction | 2012 |
| Critical Care Air Ltd | Health & social care | 2011 |