| Cleanmyoffice Ltd | Administrative & support | 2025 |
| Cleanright UK Cleaning Services Ltd | Extraterritorial | 2018 |
| Clear Automotive Locksmith Ltd | Manufacturing | 2025 |
| Clear Course Co Ltd | Information & communication | 2025 |
| Clear EAR East Ltd | Health & social care | 2023 |
| Clear Path Academy Ltd | Education | 2025 |
| Clear Skin Beauty Ltd | Other services | 2021 |
| Clear Skin Enhancements Ltd | Other services | 2024 |
| Clear Treasury Consulting Ltd. | Financial services | 2015 |
| Clear Treasury Group Limited | Financial services | 2015 |
| Clear Treasury Holdings Limited | Financial services | 2020 |
| Clearbalance Technologies Limited | Information & communication | 2026 |
| Clearbox Consulting Trustees Limited | Administrative & support | 2025 |
| Cleareaze Limited | Water & waste | 2026 |
| Clearer Waters Therapy Limited | Health & social care | 2024 |
| Clearheal Ltd | Wholesale & retail | 2022 |
| Clearing Room Ltd | Wholesale & retail | 2026 |
| Clearmark Media Ltd | Professional & scientific | 2026 |
| CLEARPATH7 Ltd | Professional & scientific | 2024 |
| Clearpave Surfacing Ltd | Administrative & support | 2013 |
| Cleartrackr Ltd | Information & communication | 2026 |
| Clements Trading Ltd | Wholesale & retail | 2017 |
| Clemora Ltd | Professional & scientific | 2026 |
| Clen Limited | Health & social care | 2019 |
| Clerigo Limited | Wholesale & retail | 2013 |
| Clever Roofing Ltd | Construction | 2019 |
| Cleverowl Solutions Ltd | Information & communication | 2026 |
| CLF Project Management Limited | Professional & scientific | 2022 |
| CLI 2019 Limited | Administrative & support | 2019 |
| Cli-Mate Trade Limited | Wholesale & retail | 2011 |
| Click Pro Ltd | Professional & scientific | 2026 |
| Clickin IT Online Limited | Wholesale & retail | 2023 |
| Clickor Ltd | Information & communication | 2023 |
| Clickpulse Limited | Professional & scientific | 2025 |
| Clicksuites Ltd | Hospitality | 2024 |
| Clifford Essex Music Co. Ltd. | Wholesale & retail | 2007 |
| Clifford Powell Consulting Ltd | Professional & scientific | 2023 |
| Clikapad Limited | Information & communication | 2005 |
| Climate Change News Limited | Information & communication | 2015 |
| Climate Fresk UK CIC | Professional & scientific | 2025 |
| Climate Home News Limited | Professional & scientific | 2018 |
| Climbwell CIC | Education | 2024 |
| Climemet Ltd | Administrative & support | 2014 |
| CLINIC31 Ltd | Education | 2023 |
| Clinical Coaching Care Limited | Public administration | 2025 |
| Clinical Research Nexus Limited | Professional & scientific | 2023 |
| Clinician People Ltd | Information & communication | 2024 |
| Clinks | Other services | 1998 |
| Clipping Path Adept Ltd | Information & communication | 2021 |
| Cliq Mirror Limited | Wholesale & retail | 2024 |
| CLM Advisory Limited | Professional & scientific | 2025 |
| Cloak Productions Limited | Information & communication | 2002 |
| Clock END Property Investments Ltd | Real estate | 2024 |
| Clock Repair Limited | Administrative & support | 2011 |
| Clockwork Transport Ltd | Transport & logistics | 2020 |
| Clora Investments Limited | Hospitality | 2021 |
| Cloud Circuit Ltd | Administrative & support | 2025 |
| CLOUD28 Ltd | Information & communication | 2021 |
| Cloudexam Ltd | Information & communication | 2026 |
| Cloudfields Ltd | Information & communication | 2023 |
| Cloudlens Limited | Information & communication | 2025 |
| Cloudstro Limited | Professional & scientific | 2024 |
| Club Bingo Ltd | Hospitality | 2026 |
| Clubroomr Limited | Information & communication | 2026 |
| Clued Community Interest Company | Other services | 2021 |
| Clutch Autocare Ltd | Wholesale & retail | 2025 |
| CM and H Limited | Professional & scientific | 2026 |
| CM Digital Solutions Ltd | Information & communication | 2025 |
| CM Operations Ltd | Professional & scientific | 2026 |
| CMA Business Consultants Limited | Professional & scientific | 2009 |
| Cmgs Group Ltd | Professional & scientific | 2025 |
| CMH Media Ltd | Professional & scientific | 2025 |
| CMK Assured Heating and Plumbing Ltd | Construction | 2018 |
| CML Consultancy Ltd | Professional & scientific | 2020 |
| CMX Design Limited | Professional & scientific | 2026 |
| CNC 24 Limited | Manufacturing | 2023 |
| CNC Machine Tool Repair Limited | Manufacturing | 2024 |
| CNE Direct UK Ltd | Wholesale & retail | 2026 |
| CNJ Maritime Ltd | Transport & logistics | 2026 |
| Cnrv Limited | Other services | 2023 |
| Coached by AC Ltd | Arts & recreation | 2025 |
| Coaching Through Life Limited | Professional & scientific | 2023 |
| Coastal Registrations Ltd | Wholesale & retail | 2022 |
| Coastline Furs CIC | Arts & recreation | 2025 |
| Coastside Relocations Limited | Real estate | 2024 |
| Coates Carbon Solutions Ltd | Professional & scientific | 2025 |
| Coates Monteiro Ltd | Real estate | 2025 |
| Coating Investments Ltd | Energy | 2025 |
| Coating Systems (International) Limited | Manufacturing | 1994 |
| Coatings Install UK Ltd | Construction | 2025 |
| Cobalt Code Ltd | Information & communication | 2025 |
| Cobb Close Management Limited | Households | 2005 |
| Cobb House Management Company Limited | Households | 2020 |
| Cobblestamp Ltd | Information & communication | 2025 |
| Cobbold Maintenance Limited | Construction | 2023 |
| Cobley Co Limited | Professional & scientific | 2026 |
| Cobley Co OPS Limited | Professional & scientific | 2026 |
| Cockfield Consulting Ltd | Professional & scientific | 2022 |
| Cockfield Developments Ltd | Construction | 2022 |
| Cockle Bay Outdoor Stove Co. Limited | Wholesale & retail | 2020 |