| City West Digital CIC | Information & communication | 2020 |
| Citygate Property Holdings Ltd | Construction | 2015 |
| Citymark Ltd | Financial services | 2008 |
| Civil Property Services Ltd | Construction | 2025 |
| Ciwa Limited | Water & waste | 2015 |
| Cixi Alpha Bearing Company Limited | Extraterritorial | 2018 |
| Cixi City Sharmoon Electric Co., Ltd | Extraterritorial | 2022 |
| Cixi Golden Star Bearing Co., Ltd | Manufacturing | 2013 |
| Cixi Jimax Industry Co., Ltd. | Wholesale & retail | 2015 |
| Cixi Meka Machine Parts Co., Ltd | Extraterritorial | 2019 |
| Cjch Financial Limited | Financial services | 2015 |
| CJD Accounting Limited | Professional & scientific | 2014 |
| CK Global Services Co., Ltd | Manufacturing | 2023 |
| CKP Services Limited | Construction | 2015 |
| CL Coastline Limited | Wholesale & retail | 2022 |
| Claire Pure Trading Limited | Manufacturing | 2025 |
| Clairvoyant Advisory Ltd | Professional & scientific | 2025 |
| Clan Works Ceramics Limited | Arts & recreation | 2012 |
| Clapham Studios Ltd | Professional & scientific | 2016 |
| Clara Terra Holdings Limited | Financial services | 2026 |
| Clarity Health Coaching Ltd | Health & social care | 2025 |
| Clarity Mortgages Limited | Financial services | 2007 |
| Clarks Bulk Haulage Ltd | Transport & logistics | 2023 |
| Clarkus Limited | Information & communication | 2018 |
| Clasique Ltd | Wholesale & retail | 2025 |
| Classbro Ltd | Education | 2021 |
| Classchoice Real Estates Limited | Real estate | 2021 |
| Classical Records London Limited | Wholesale & retail | 2020 |
| Clay Days London Ltd | Arts & recreation | 2022 |
| Cldf Limited | Administrative & support | 2016 |
| Cleaning Services (South London) Limited | Real estate | 1983 |
| Clear Bright Consulting Ltd | Professional & scientific | 2015 |
| Clear Education Solutions Limited | Information & communication | 2025 |
| Clear Financial Advice Limited | Financial services | 2001 |
| Clear Path Semi-Independent Living Limited | Health & social care | 2022 |
| Clear Water Co., Ltd | Wholesale & retail | 2016 |
| Clearcom Solutions Ltd | Information & communication | 2026 |
| Cleen Trading Company Limited | Wholesale & retail | 2021 |
| Clermon ET Associes Limited | Manufacturing | 2025 |
| Clever Claws Pets Services Ltd | Other services | 2024 |
| Cleves Place Limited | Real estate | 2008 |
| Click Money Limited | Extraterritorial | 2012 |
| Clifford Publishing Limited | Information & communication | 2019 |
| Clifftonvilla Consultants Ltd | Professional & scientific | 2011 |
| Climatech Industries Co., Ltd | Extraterritorial | 2011 |
| CLM Moves Ltd | Transport & logistics | 2020 |
| Clock House Mortgages Limited | Financial services | 2011 |
| Clock House Nail Limited | Other services | 2023 |
| Clockhouse Cars Limited | Transport & logistics | 2004 |
| Clockhouse PM Ltd | Administrative & support | 2016 |
| Cloud Agnostic Coding Limited | Administrative & support | 2022 |
| Cloud Internet Service Limited | Information & communication | 2021 |
| Cloud Sparkle Co., Ltd. | Extraterritorial | 2025 |
| Cloud Stone Group Limited | Wholesale & retail | 2021 |
| Cloud Travel Frog Company Limited | Information & communication | 2021 |
| Cloudbook International Co., Ltd | Manufacturing | 2020 |
| Cloudlink Technology (UK) Limited | Manufacturing | 2022 |
| Cloudtalent Stone Ltd | Wholesale & retail | 2021 |
| Clover Nails Ltd | Other services | 2025 |
| Cloverleaves Limited | Wholesale & retail | 2020 |
| Club Alpine Ltd | Administrative & support | 2022 |
| Club Langley Bar Services Limited | Hospitality | 2007 |
| CLX Manufacturing Co., Ltd | Wholesale & retail | 2018 |
| Clyinland Co., Ltd | Information & communication | 2023 |
| CM & UZ Styles Ltd | Wholesale & retail | 2026 |
| CM Beck Limited | Real estate | 2018 |
| CM Pavilions Limited | Real estate | 2022 |
| CMA Design Limited | Professional & scientific | 2018 |
| CMB Media Limited | Professional & scientific | 2025 |
| Cmda Limited | Manufacturing | 2020 |
| CMS Property Services Ltd | Real estate | 2017 |
| CNC Searches Limited | Administrative & support | 2010 |
| Cnchess Co., Ltd | Extraterritorial | 2020 |
| CND Resource Limited | Manufacturing | 2024 |
| CNH Engineering Ltd | Professional & scientific | 2022 |
| CNJ International Co., Ltd | Extraterritorial | 2012 |
| Cntc Project Management Ltd | Professional & scientific | 2024 |
| CNW International Limited | Wholesale & retail | 2007 |
| Co-Creating Ltd | Administrative & support | 2022 |
| Co-Pour Ltd | Professional & scientific | 2017 |
| Coach Communications Limited | Administrative & support | 2024 |
| Coaching Potential Limited | Education | 2016 |
| Coalesce & Bonds International Ltd | Other services | 2020 |
| Coalpot Ventures Ltd | Manufacturing | 2012 |
| Coastal Lake 2019 Ltd | Hospitality | 2019 |
| Coastway Rugs Ltd | Wholesale & retail | 2022 |
| Cobalt Delivery Limited | Professional & scientific | 2018 |
| Cobalt Property Portfolio Ltd | Real estate | 2023 |
| Cobra Concrete Ltd. | Construction | 2000 |
| Cobtec UK Co., Ltd | Manufacturing | 2023 |
| Cocoa Shirin Limited | Information & communication | 2011 |
| Codewave Software UK Limited | Information & communication | 2024 |
| Codooro Group (UK) Ltd | Manufacturing | 2017 |
| Coffee HIT Limited | Wholesale & retail | 2007 |
| Coffee X Ltd | Manufacturing | 2017 |
| Cogency Analysis & Research Limited | Professional & scientific | 2018 |
| Cognisheets Ltd | Information & communication | 2024 |
| Coinmix Global Ltd | Information & communication | 2021 |
| Cokelife International Trading Co., Ltd | Extraterritorial | 2021 |
| Colaba Limited | Hospitality | 2019 |