| Circle of Beautiful People International Ltd | Arts & recreation | 2020 |
| Circle Surveyors Ltd | Professional & scientific | 2021 |
| Cirqon Technologies Limited | Information & communication | 2025 |
| Cirrus Electrical Services (South West) Limited | Construction | 2010 |
| Ciso-Office Ltd | Information & communication | 2022 |
| Citi Utilities Limited | Construction | 2009 |
| Citilodge Limited | Hospitality | 2004 |
| City and Shire Electrical Services Limited | Construction | 2018 |
| City Cars Taxis and Private Hire Ltd | Transport & logistics | 2019 |
| City Fire Protection Limited | Manufacturing | 2003 |
| City of Batticaloa SL Limited | Health & social care | 2024 |
| Civicedge Contractors Ltd | Construction | 2023 |
| Civil Technologies Limited | Construction | 2011 |
| CJ Landscapes Services Ltd | Administrative & support | 2025 |
| CJ Tech Solution Limited | Professional & scientific | 2023 |
| CJ Wood Property Group Ltd | Real estate | 2023 |
| CJG Medical Services Ltd | Health & social care | 2024 |
| CJH Event Management Ltd | Professional & scientific | 2021 |
| CJS Engineering Limited | Professional & scientific | 2004 |
| CK Business Academy Ltd | Professional & scientific | 2026 |
| CK Properties ( Glos) Limited | Real estate | 2024 |
| CK Skin Clinic Limited | Other services | 2022 |
| CK Technical Solutions Ltd | Information & communication | 2024 |
| CKF Holdings Limited | Professional & scientific | 2002 |
| CKF Management Company Limited | Professional & scientific | 2020 |
| CKF Systems Limited | Manufacturing | 1988 |
| CL Business Limited | Hospitality | 2021 |
| CL Danter Ltd | Arts & recreation | 2023 |
| Cl.Locuming Ltd | Professional & scientific | 2017 |
| CLA Mediation and Training Ltd | Professional & scientific | 2024 |
| Claire Calder Consultancy Limited | Education | 2022 |
| Clapham Consulting Ltd | Professional & scientific | 2020 |
| Clapham Junction Taverns Ltd | Hospitality | 2021 |
| Clapham Leisure Ltd | Hospitality | 2013 |
| Clapham Old Town Taverns Ltd | Hospitality | 2022 |
| Clapham Payroll Ltd | Administrative & support | 2017 |
| Claremont Homes (Newsham) | | 1999 |
| Clarence Anaesthesia Limited | Health & social care | 2019 |
| Clarendon and Mulberry Properties Ltd | Real estate | 2019 |
| Clarity Advisory Ltd | Professional & scientific | 2023 |
| Clarity Branding Ltd | Information & communication | 2025 |
| Clarity Hearing Holdings Limited | Financial services | 2025 |
| Clark Holdings (UK) Limited | Financial services | 2013 |
| Clark Machinery Services Limited | Manufacturing | 2011 |
| Clark-Milbourne Limited | Professional & scientific | 2011 |
| Clarke and Sons Property Ltd | Real estate | 2018 |
| Clarke Brothers Properties Limited | Real estate | 2020 |
| Clarkson Evans Group Limited | Financial services | 2022 |
| Clarkson Evans Holdings Limited | Professional & scientific | 2008 |
| Clarkson Evans Limited | Construction | 1999 |
| Clarkson Evans Solar Limited | Construction | 2021 |
| Clarkson Evans Training Limited | Education | 2008 |
| Clarondor Limited | Real estate | 2025 |
| Clarus Cleaning Services Ltd | Administrative & support | 2022 |
| Class Building Services Limited | Professional & scientific | 2011 |
| Class Private Hire Ltd | Transport & logistics | 2020 |
| Classic Car Plates Ltd | Wholesale & retail | 2022 |
| Classic Windows (Wiltshire) Limited | Construction | 1983 |
| Classico Caffe UK Ltd | Hospitality | 2026 |
| Classico Cotswolds Limited | Construction | 2021 |
| Classics Exchange UK Limited | Wholesale & retail | 2021 |
| CLD Sport Ltd | Arts & recreation | 2023 |
| Clean Edge Services Ltd | Administrative & support | 2026 |
| Clean Floor Machines Ltd | Administrative & support | 2017 |
| Clean on ME Limited | Administrative & support | 2020 |
| Clean Shield Professional Ltd | Administrative & support | 2009 |
| Cleanco Valeting Limited | Wholesale & retail | 2024 |
| Cleaner Experience Ltd | Administrative & support | 2025 |
| Clear and Clean House Clearance Ltd | Water & waste | 2025 |
| Clear Choice Health Care Ltd | Administrative & support | 2023 |
| Clear Construction Services Ltd | Construction | 2022 |
| Clear CUT & Secure Limited | Administrative & support | 2025 |
| Clear Lessons Limited | Information & communication | 2021 |
| Clearhold Consulting Ltd | Information & communication | 2025 |
| Clearview Investments Limited | Real estate | 2023 |
| Clearway Doors and Windows Ltd | Manufacturing | 1983 |
| Clee Event Production Ltd | Administrative & support | 2012 |
| Cleeve Hill Property Limited | Real estate | 2018 |
| Cleevely Group Ltd | Real estate | 2025 |
| Clement Property Limited | Real estate | 2020 |
| CLF Property Rental Limited | Real estate | 2023 |
| Cliff-Clocks Limited | Wholesale & retail | 2015 |
| Clifford Barnes Ltd | Construction | 2020 |
| Clifton Media Ltd | Professional & scientific | 2025 |
| Clifton Place Management Limited | Households | 1990 |
| Clint's Custom Carpentry Limited | Manufacturing | 2024 |
| Clipevents Ltd | Hospitality | 2017 |
| Clipper Sustainable Business Solutions Limited | Professional & scientific | 2024 |
| Clissold Plumbing & Heating Ltd | Construction | 2023 |
| Cloisters Reach (Residents) Management Limited | Households | 1990 |
| Close Community Management Limited | Households | 1991 |
| Close Hauled Ltd | Professional & scientific | 2024 |
| Closedbydavid Ltd | Administrative & support | 2026 |
| Cloud Appreciation Ltd | Wholesale & retail | 2006 |
| Cloud Force Marketing Ltd | Professional & scientific | 2021 |
| Cloud Innovation Pro Ltd | Information & communication | 2025 |
| Cloud Nine Support Ltd | Health & social care | 2018 |
| Cloud Plug Ltd | Wholesale & retail | 2026 |
| Clovegorge Property Management Limited | Real estate | 2006 |
| CLR Dance Ltd | Arts & recreation | 2013 |