| Chromium Assets Limited | Professional & scientific | 2009 |
| Chromium Suchex LLP | | 2009 |
| Church Cottages Management Company Limited | Extraterritorial | 1983 |
| Chutney Indian Takeaway Ltd | Hospitality | 2023 |
| CHW Accountants Limited | Professional & scientific | 2019 |
| Cibo Gusto Ltd | Hospitality | 2026 |
| Cinnamon Estates Ltd | Real estate | 2020 |
| Circle Express Specialist Services Ltd | Transport & logistics | 2009 |
| Circor SUB Ltd | Professional & scientific | 1999 |
| Circuit Automotive Limited | Other services | 2024 |
| Circus Food & Wine Ltd | Wholesale & retail | 2015 |
| Cirque Group Ltd | Professional & scientific | 2016 |
| Cirrus Connects Limited | Information & communication | 2013 |
| Cisalpina Tours UK Limited | Administrative & support | 2023 |
| Citi Electrics Ltd | Other services | 2003 |
| City Chick Ltd | Professional & scientific | 1985 |
| City Houses Limited | Administrative & support | 2007 |
| City Ledgers Ltd | Professional & scientific | 2025 |
| City Property Rentals Ltd | Real estate | 2023 |
| CITY2COUNTRY Services Ltd | Other services | 2019 |
| Cityline Airport Transfers Limited | Transport & logistics | 2025 |
| Cityline Cars Ltd | Transport & logistics | 2026 |
| Cityshield Security Services Ltd | Administrative & support | 2025 |
| Citywalk Properties Ltd | Real estate | 2021 |
| Civil Homes Ltd | Real estate | 2022 |
| Cizma Building & Construction Ltd | Administrative & support | 2019 |
| CJA Haulage Solutions Limited | Water & waste | 2020 |
| CJO Fleet Cars Ltd | Wholesale & retail | 2017 |
| CK Mortgages Limited | Financial services | 2018 |
| CKO Consulting Limited | Information & communication | 2010 |
| Clairvale Property Ltd | Real estate | 2025 |
| Clara's Cleaners Limited | Administrative & support | 2023 |
| Claremont Court (High Wycombe) Limited | Real estate | 2007 |
| Clarence Court (Firstgate) RTM Company Limited | Households | 2023 |
| Clarence Court (Uxbridge) Management Company Limited | Households | 2003 |
| Clarence Court Management Co. (Maidenhead) Limited | Real estate | 1984 |
| Clargo Electrical Services Ltd | Professional & scientific | 2023 |
| Clarity VAT Solutions Ltd | Administrative & support | 2019 |
| Clarivon Consulting Ltd | Professional & scientific | 2025 |
| Clarkes Sparks Ltd | Manufacturing | 2021 |
| Class Workwear Limited | Manufacturing | 2018 |
| Clau ROUTE66 Limited | Construction | 2025 |
| Clau Transport Ltd | Transport & logistics | 2019 |
| Claudiu Florin Ltd | Information & communication | 2024 |
| Claudiu Ltd | Construction | 2015 |
| Clayhill Green Ltd | Real estate | 2023 |
| Clbadvancedaesthetics Ltd | Wholesale & retail | 2026 |
| Cleaning Active Services Ltd | Administrative & support | 2016 |
| CLEANING4U Ltd | Administrative & support | 2021 |
| Clearblue Enterprise Ltd | Wholesale & retail | 2021 |
| Cleartech Digital Ltd | Manufacturing | 2014 |
| Cleartech Displays Ltd | Information & communication | 2018 |
| Clearwater Business and Financial Planning Limited | Professional & scientific | 1996 |
| Clelland Cars Ltd | Wholesale & retail | 2021 |
| Clementine Close Management Company Limited | Households | 1988 |
| Clemtree Limited | Extraterritorial | 2005 |
| Clene Ltd | Administrative & support | 2026 |
| Cleveland Street Freehold Management Limited | Households | 2019 |
| Clever Accountants for Business Limited | Professional & scientific | 2025 |
| Clewer ST Stephen Property Management Limited | Real estate | 1999 |
| Clewer ST. Stephen Property Limited | Real estate | 1999 |
| Click Law 24 Limited | Professional & scientific | 2010 |
| Client Partners Global Limited | Professional & scientific | 2012 |
| Clifford House Limited | Health & social care | 1997 |
| Cliften Properties Ltd | Real estate | 2024 |
| Clifton Park Residential Ltd | Real estate | 2016 |
| Climexa AI Ltd | Energy | 2025 |
| Clive S Norman and Associates Limited | Administrative & support | 1998 |
| CLJ Ltd | Professional & scientific | 2018 |
| Cloud IT Consultant UK Ltd | Information & communication | 2020 |
| Cloud IX Kitchens Ltd | Hospitality | 2020 |
| Cloudaxis Solutions Ltd | Wholesale & retail | 2026 |
| Cloudberry Technologies Limited | Information & communication | 2013 |
| CLOUDBERRY360 Digital Limited | Wholesale & retail | 2025 |
| Cloudsprint Limited | Information & communication | 2017 |
| Cloudstake Limited | Real estate | 2024 |
| CLOUDVISION365 Ltd | Information & communication | 2025 |
| Clove Preservations Ltd | Construction | 2024 |
| Clowns of GOD Ltd | Wholesale & retail | 2025 |
| Clrt Services Ltd | Extraterritorial | 2017 |
| Club Class Carriages Limited | Transport & logistics | 2015 |
| CM Consultancy Group Ltd | Professional & scientific | 2025 |
| Cm&E Solutions Limited | Professional & scientific | 2016 |
| CMF Developments Ltd | Construction | 2019 |
| Cmjpainters Ltd | Construction | 2025 |
| CMY001 Ltd | Financial services | 2022 |
| CN Cargo Limited | Transport & logistics | 2021 |
| CNC Production Limited | Information & communication | 2017 |
| Cnet Design Limited | Professional & scientific | 2013 |
| Cnooc Ettrick U.K. Limited | Mining & quarrying | 2000 |
| Cnooc GAS and Power UK Trading Limited | Wholesale & retail | 2025 |
| Cnooc Petroleum Europe Limited | Mining & quarrying | 1972 |
| Cnooc Petroleum Farragon U.K. Limited | Mining & quarrying | 2005 |
| Cnooc UK Limited | Administrative & support | 2013 |
| Co&T - Prime Business Services Ltd | Professional & scientific | 2024 |
| Coach House Management Company (Wooburn Green) Limited(The) | Real estate | 1987 |
| Coach My Future Ltd | Administrative & support | 2024 |
| Coached by Hannah Ltd | Arts & recreation | 2022 |
| Coachhub Ltd | Financial services | 2022 |
| Coastline Stays Limited | Real estate | 2025 |