| Churchill Lodge Management Company Limited | Households | 2002 |
| Churchill Properties Ltd | Real estate | 2023 |
| Churn Meadows Management Company Limited | Households | 2007 |
| Churn River Limited | Administrative & support | 2010 |
| Churnside Estate Limited | Households | 2001 |
| Chymicus UK Limited | Administrative & support | 2022 |
| Cibus-Terrae Limited | Health & social care | 2013 |
| Cider by Baynes Ltd | Manufacturing | 2020 |
| CIG Logistics Ltd | Construction | 2026 |
| CIL Education Ltd | Education | 2012 |
| Cilfynydd NG Limited | Energy | 2023 |
| Cilta Holdings Ltd | Professional & scientific | 2022 |
| Cinemission Productions Limited | Information & communication | 2009 |
| Cinnlois 08 Limited | Extraterritorial | 2020 |
| Cinnlois Limited | Real estate | 2020 |
| Cinzia Cordella Ltd | Professional & scientific | 2015 |
| Ciprian Cosofret Limited | Information & communication | 2016 |
| Circle 2 Success Limited | Other services | 2013 |
| Circle Consult Ltd | Professional & scientific | 2022 |
| Circle Residential Management Ltd | Real estate | 2004 |
| Circonix Limited | Extraterritorial | 1979 |
| Circus Day Nursery Limited | Administrative & support | 2005 |
| Cirencester Self Storage Limited | Administrative & support | 2005 |
| Cirrus Aqua Limited | Construction | 2005 |
| Cirrus Business Solutions Limited | Professional & scientific | 2006 |
| Cirrus Cloud Accounting Limited | Professional & scientific | 2013 |
| Cirrus Software Solutions Limited | Information & communication | 2022 |
| Citi Utilities Holdings Limited | Financial services | 2024 |
| Citrus Seating Ltd | Manufacturing | 2014 |
| City Apartments MK Ltd. | Hospitality | 2007 |
| City Paving South-West Limited | Construction | 2007 |
| City Property Management (Gloucester) Limited | Construction | 2024 |
| CJ Bailey Limited | Administrative & support | 2015 |
| CJ Eats Limited | Hospitality | 2024 |
| CJ Sparkle Cleaning Services Ltd | Administrative & support | 2026 |
| CJ Unit Ltd | Real estate | 2018 |
| CJ Valeting Ltd | Administrative & support | 2022 |
| Cjacomms Ltd | Information & communication | 2026 |
| CJR Staffing Ltd | Administrative & support | 2023 |
| Cjsealants Ltd | Construction | 2026 |
| CK Cricket Club Limited | Arts & recreation | 2014 |
| CK Landscaping Ltd | Administrative & support | 2025 |
| CKI Interiors Ltd | Manufacturing | 2023 |
| CL Furnished Lettings Ltd | Real estate | 2018 |
| CLA Enterprises Limited | Education | 2022 |
| Cladswell Developments Limited | Construction | 2014 |
| Claim Support Co Ltd | Administrative & support | 2025 |
| Claim Validation Technologies Limited | Extraterritorial | 2011 |
| Claire Booth Cooks Events Limited | Hospitality | 2023 |
| Claire Croft Associates Ltd | Information & communication | 2016 |
| Claire Halstead Interiors Ltd | Professional & scientific | 2024 |
| Claire Kennedy Design Limited | Professional & scientific | 2025 |
| Claparo Innovations Limited | Manufacturing | 2019 |
| Clare Haggas Fine Art & Designs Ltd | Wholesale & retail | 2018 |
| Clarence Square Management Limited | Households | 1985 |
| Clarence Square Residents Association Limited | Households | 1992 |
| Clareseed.Com Ltd | Administrative & support | 2025 |
| Clari U.K. Limited | Administrative & support | 2019 |
| Claria Consulting Ltd | Administrative & support | 2012 |
| Claridge Aesthetics Limited | Other services | 2024 |
| Clarion Insight Limited | Information & communication | 2015 |
| Clarity Consruction Group Ltd | Construction | 2025 |
| Clarity Space Limited | Professional & scientific | 2009 |
| Clark Development and Holding Limited | Real estate | 2014 |
| Clark Family Property LLP | | 2022 |
| Clark Wealth Management Ltd | Professional & scientific | 2018 |
| Clarke & Humphries Ltd | Construction | 2011 |
| Clarke Software Services Limited | Information & communication | 1998 |
| Clarus Consulting Limited | Professional & scientific | 2005 |
| Clarvex Finance Ltd | Administrative & support | 2026 |
| Classic Buicks Ltd | Administrative & support | 2018 |
| Classic Car Leds Ltd | Wholesale & retail | 2019 |
| Classic Collector Services Ltd | Wholesale & retail | 2024 |
| Classic Dispensers Ltd | | 1988 |
| Classic Joinery Limited | Construction | 2023 |
| Classified Films Limited | Information & communication | 2016 |
| Classy Cotswold Cottages Limited | Real estate | 2020 |
| Classy Curls Ltd | Other services | 2026 |
| Clavell & Hind Limited | Manufacturing | 2022 |
| Clay Club Skincare Limited | Manufacturing | 2018 |
| Clay Labs Digital Ltd | Wholesale & retail | 2022 |
| Claybury Consultancy Limited | Information & communication | 2016 |
| CLC Developments (Cheltenham) Limited | Construction | 2019 |
| CLC Services Limited | Real estate | 1992 |
| Clean First Ltd | Administrative & support | 2023 |
| Cleanacres Machinery Limited | Manufacturing | 1978 |
| Cleanmaster Services Limited | Administrative & support | 2020 |
| Cleanology Ltd | Administrative & support | 2025 |
| Cleanwave Solutions Ltd | Information & communication | 2008 |
| Cleanzali Limited | Administrative & support | 2026 |
| Clear Accounts Ltd | Professional & scientific | 2011 |
| Clear Advantage Ltd | Information & communication | 1997 |
| Clear B2B Marketing & PR Ltd | Professional & scientific | 1989 |
| Clear Chroma Limited | Information & communication | 2021 |
| Clear Conveyancing Limited | Professional & scientific | 2025 |
| Clear Natural Spas Limited | Wholesale & retail | 2005 |
| Clearchoice Windows, Doors & Glazing Ltd | Construction | 2019 |
| Clearly Orthodontics Limited | Health & social care | 2014 |
| Clearq Consulting Limited | Other services | 2017 |
| Clearwater Connect Ltd | Professional & scientific | 2025 |