| Chatham Place (Phase 1) Estate Manco Limited | Administrative & support | 2004 |
| Chattlewell Limited | Construction | 1991 |
| Chediston Partners LLP | | 2016 |
| Cherish PR Limited | Professional & scientific | 2003 |
| Cherry Hill Properties Limited | Real estate | 2019 |
| Cherubs Floral Design Ltd | Wholesale & retail | 2004 |
| Cherwell House Residents Limited | Households | 2017 |
| Chevron Research Limited | Professional & scientific | 2023 |
| Chill OUT Holdings Ltd | Financial services | 2020 |
| Chiltern Court Wallingford Road M.C. Limited | Households | 2008 |
| Chiltern Cycles Ltd | Administrative & support | 2026 |
| Chiltern Trains Ltd | Administrative & support | 2011 |
| Chilterns Stewardship Ltd | Real estate | 2026 |
| Chocolate Mobile Limited | Information & communication | 2007 |
| Choiceblock Property Management Limited | Households | 1988 |
| Cholsey Fair Mile Limited | Households | 2018 |
| Christopher Howie International Ltd | Administrative & support | 2011 |
| Circle Massage Therapy Limited | Other services | 2017 |
| Citrus Media Limited | Information & communication | 2002 |
| Civil Designer UK Limited | Information & communication | 2017 |
| CJ Armstrong Landscaping and Groundwork Ltd | Administrative & support | 2018 |
| CKM3 Advisory Ltd | Professional & scientific | 2023 |
| CKM3 Holdings Ltd | Financial services | 2023 |
| CKM3 Investments Ltd | Financial services | 2023 |
| Classic Car Sales Limited | Wholesale & retail | 2005 |
| CLB Technology With Care Ltd | Information & communication | 2013 |
| Clean and Shiny Henley Ltd | Wholesale & retail | 2025 |
| Cleaning Angels 12 Ltd | Administrative & support | 2019 |
| Clear Sight Developments Limited | Construction | 2025 |
| Clifton Car Sales Limited | Wholesale & retail | 2018 |
| Cloud 100 Ltd | Information & communication | 2014 |
| CMI and Partners Limited | Professional & scientific | 1997 |
| Coachteam Ltd | Professional & scientific | 2023 |
| Cobo PR Ltd | Information & communication | 2019 |
| Coco Create Limited | Professional & scientific | 2016 |
| Code Fairy Ltd | Information & communication | 2022 |
| Coffee Lady Ltd | Hospitality | 2017 |
| Cohno Limited | Manufacturing | 2022 |
| Coins and Glass Limited | Wholesale & retail | 2013 |
| Colecar Stategic Land (M1/J12) Ltd | Construction | 2025 |
| Colecar Strategic Land (Aston END) Ltd | Construction | 2025 |
| Colecar Strategic Land (Bidwell) Ltd | Construction | 2025 |
| Colecar Strategic Land (Brickfield Stud) Ltd | Construction | 2025 |
| Colecar Strategic Land (Creaton) Ltd | Construction | 2025 |
| Colecar Strategic Land (Irchester) Ltd | Construction | 2023 |
| Colecar Strategic Land (North Crawley) Ltd | Construction | 2025 |
| Colecar Strategic Land (Raunds) Ltd | Construction | 2025 |
| Colecar Strategic Land (Shrivenham) Ltd | Construction | 2025 |
| Colecar Strategic Land (Strawberry Fields Stud) Ltd | Construction | 2025 |
| Colecar Strategic Land (Swaffham) Ltd | Construction | 2025 |
| Colecar Strategic Land (York) Limited | Construction | 2025 |
| Colecar Strategic Land Arlesy 1 Limited | Construction | 2025 |
| Colecar Strategic Land(Newton Flotman) Ltd | Construction | 2025 |
| Collco Trading Limited | Wholesale & retail | 2002 |
| Collective Brand Studio Limited | Wholesale & retail | 2023 |
| Collin & Associates Ltd | Professional & scientific | 2024 |
| Collingbourne Estate Management Limited | Construction | 2022 |
| Colltec Solutions Ltd. | Construction | 2016 |
| Commercial Holdings Limited | Real estate | 2003 |
| Common Ground Estate & Property Management Limited | Real estate | 2010 |
| Compare the Car Parking Ltd | Transport & logistics | 2023 |
| Compliance Xchange Limited | Professional & scientific | 2017 |
| Composearch LLP | | 2010 |
| Compound Equity Group Limited | Professional & scientific | 2021 |
| Compression Therapy UK Ltd. | Professional & scientific | 2013 |
| Concru Consulting Ltd | Information & communication | 2026 |
| Concussion Toolkit Ltd | Professional & scientific | 2024 |
| Coniston Services Limited | Professional & scientific | 2005 |
| Connaught Surveying Ltd | Professional & scientific | 2020 |
| Consekense Ltd | Professional & scientific | 2011 |
| Constanza Search Ltd | Administrative & support | 2012 |
| Conway & Co. Ltd | Agriculture & fishing | 2021 |
| Conygre Consulting Limited | Professional & scientific | 2018 |
| Cool-Properties Limited | Real estate | 2015 |
| Copado Limited | Professional & scientific | 2018 |
| Coppid Farming Enterprises LLP | | 2011 |
| Coptic Holdings Limited | Professional & scientific | 1988 |
| Cornwall Honey Co. Ltd | Agriculture & fishing | 2025 |
| Coronet Computers Services Limited | Information & communication | 1988 |
| Coscientia Ltd | Professional & scientific | 2016 |
| Cosec Compliance Limited | Information & communication | 2005 |
| Cosy Nook Inns Limited | Hospitality | 2025 |
| Cote Management Ltd | Households | 2018 |
| Cotswold Cloche Ltd | Information & communication | 2024 |
| Country Roofing Supplies (2001) Ltd | Wholesale & retail | 2002 |
| Country Touring Ltd | Transport & logistics | 2021 |
| County Cars Executive Limited | Transport & logistics | 2017 |
| Countywide Estates Limited | Real estate | 2013 |
| Courtiers Asset Management Limited | Financial services | 2014 |
| Courtiers Group Holdings Limited | Administrative & support | 2016 |
| Courtiers Investment Services Limited | Financial services | 1978 |
| Courtiers Trustees Limited | Financial services | 2008 |
| Covered in JAM CIC | Administrative & support | 2023 |
| Cranford Consultancy Services Limited | Professional & scientific | 2018 |
| Crausaz Wordsworth Group Ltd | Financial services | 2023 |
| Crave Creative Ltd | Professional & scientific | 2019 |
| Crazies Hall Estate Management Ltd | Real estate | 2025 |
| Creative Design (Architectural) Limited | Extraterritorial | 2013 |
| Creative Henley CIC | Arts & recreation | 2026 |
| Creative Photography Professionals Limited | Professional & scientific | 2023 |