| Churchill Waste Services Limited | Water & waste | 2020 |
| Cicada Destinations Ltd | Administrative & support | 2022 |
| CIK Homes Ltd | Real estate | 2020 |
| Cini Property Limited | Households | 2020 |
| Ciphernet Solutions Limited | Information & communication | 2025 |
| Circularity Energy Limited | Professional & scientific | 2022 |
| Circularity Water Ltd | Professional & scientific | 2024 |
| Citizens Cars Ltd | Transport & logistics | 2018 |
| City CAP Limited | Health & social care | 2011 |
| City Crest Living Limited | Real estate | 2024 |
| City Hawk Ltd | Professional & scientific | 2023 |
| City Trax Limited | Information & communication | 2022 |
| Citygold Commercial Funding Limited | Professional & scientific | 2009 |
| Citygold Financial Services Limited | Financial services | 2009 |
| Citygold Properties Limited | Real estate | 2024 |
| Cityscape Contracting Ltd | Construction | 2023 |
| CJ JET Washing Ltd | Administrative & support | 2024 |
| CJ Premium Valeting Ltd | Administrative & support | 2023 |
| Cjsills Contracting Limited | Professional & scientific | 2016 |
| CJT Compliance Limited | Professional & scientific | 2024 |
| CK Automotive Specialists Ltd | Wholesale & retail | 2020 |
| CK Financial Markets Limited | Administrative & support | 2006 |
| Ckvl Self Build Limited | Construction | 2023 |
| CKW Limited | Construction | 2015 |
| CL Interiors Ltd | Construction | 2020 |
| Claims Compo Limited | Professional & scientific | 2023 |
| Claire V Cole Limited | Health & social care | 2015 |
| Claireabelle Flowers Limited | Wholesale & retail | 2023 |
| Clanfield Barbers Ltd | Other services | 2026 |
| Clanfield Cricket Club Limited | Arts & recreation | 2023 |
| Clanfield Mohol Ltd | Hospitality | 2025 |
| Clanfield Spice Limited | Hospitality | 2023 |
| Clanfield Stores Ltd | Wholesale & retail | 2016 |
| Claremont Gardens Financial Services Ltd | Financial services | 2020 |
| Clarendon Close Management Company Limited | Hospitality | 2003 |
| Clarion Design Services Ltd | Manufacturing | 2000 |
| Clark King Ltd | Real estate | 2024 |
| Clarke Installations Limited | Administrative & support | 2026 |
| Clarke Taylor Group Limited | Wholesale & retail | 2020 |
| Clase Connected Ltd | Wholesale & retail | 1995 |
| Classic London Services Limited | Extraterritorial | 2013 |
| Classic Yacht Services Ltd | Manufacturing | 2022 |
| Classical Services Limited | Information & communication | 2019 |
| Classics by Jswl Limited | Wholesale & retail | 2014 |
| Claygate Ventures Limited | Construction | 2025 |
| Claymill Fencing Ltd | Administrative & support | 2022 |
| Cldj UK Consultants Ltd | Professional & scientific | 2023 |
| Clean & Clear Exteriors Limited | Administrative & support | 2025 |
| Clean Air Traders Ltd | Financial services | 2023 |
| Clean and Shine Services Ltd | Administrative & support | 2023 |
| Cleanteam Services Ltd | Administrative & support | 2022 |
| Clear Links Holdings Limited | Other services | 2019 |
| Clear Links Limited | Professional & scientific | 2014 |
| Clear Links Support Ltd. | Administrative & support | 2006 |
| Clear Links Technologies Limited | Administrative & support | 2014 |
| Clear Minds Psychotherapy Ltd | Professional & scientific | 2025 |
| Clear Stack Ltd | Information & communication | 2025 |
| Clearly Secure Locks & Glazing Ltd | Construction | 2021 |
| Clearspot Media Limited | Information & communication | 2026 |
| Cleat Medical Limited | Education | 2022 |
| Clementine 2020 Limited | Wholesale & retail | 2020 |
| Clementine Creative Limited | Professional & scientific | 2007 |
| Clements Estates Limited | Administrative & support | 2007 |
| Clements Technical Recruitment Limited | Administrative & support | 1998 |
| Clia Construction Ltd | Construction | 2024 |
| Click N Plumb Ltd | Construction | 2024 |
| CLICK4ELECTRICS Ltd | Wholesale & retail | 2016 |
| Client Consultancy Services Limited | Real estate | 2004 |
| Cliff Phillips Landscapes Ltd | Construction | 2025 |
| Climate Cooling & Heating Ltd | Energy | 2025 |
| Climate GAS Services Limited | Construction | 2023 |
| Climate Supply Ltd | Construction | 2013 |
| Climatech Group Ltd | Construction | 2019 |
| Climatech Ltd | Construction | 2012 |
| Climax Real Estate Ltd | Real estate | 2023 |
| Clinical Massage London Limited | Health & social care | 2026 |
| Clinton Electrics Limited | Administrative & support | 2010 |
| Clio Property Investments Ltd | Real estate | 2022 |
| Clock Tower Southsea Ltd | Hospitality | 2022 |
| Clockaudio Limited | Manufacturing | 1994 |
| Clockhouse 220 Management Company Ltd | Households | 2014 |
| Clomec Care Ltd | Health & social care | 2022 |
| CLOSE2HOME.4PROPERTY Limited | Real estate | 2019 |
| Cloudevo Ltd | Information & communication | 2025 |
| CLR Property Services Ltd | Real estate | 2026 |
| CLR Scaffolding Limited | Construction | 2015 |
| CLS Corporate 1 Limited | Financial services | 2025 |
| CLS Corporate 2 Limited | Financial services | 2025 |
| CLS Corporate 3 Limited | Professional & scientific | 2025 |
| CLS Installations (Haslemere) Ltd | Construction | 2021 |
| CLUB36 Collective Limited | Wholesale & retail | 2025 |
| Clubconnectmedia Limited | Professional & scientific | 2023 |
| Clumos Limited | Information & communication | 2024 |
| Clyde AI Limited | Information & communication | 2025 |
| CM Automotive Ltd | Wholesale & retail | 2026 |
| CM ROV Systems Ltd | Manufacturing | 2025 |
| CMB Civils Limited | Construction | 2023 |
| CMI Rail Services Ltd | Transport & logistics | 2022 |
| CMM Electrical Services Limited | Construction | 2016 |
| CNC Eco Logistics Limited | Transport & logistics | 2025 |