| Clear Alignment Ltd | Professional & scientific | 2018 |
| Clear Link Consultancy Ltd | Administrative & support | 2021 |
| Clear Star Group Limited | Professional & scientific | 2023 |
| Clearpath Wills and Estate Planning Ltd | Other services | 2023 |
| Clearsense Marketing Limited | Information & communication | 2010 |
| Clearspace Learning Ltd | Education | 2024 |
| Clearvue Cleaning Ltd | Administrative & support | 2023 |
| Clearway Sales and Promotions Ltd | Manufacturing | 2004 |
| Cledwin Limited | Wholesale & retail | 2023 |
| Cleenol Group Limited | Manufacturing | 1959 |
| Cleenol Holdings Limited | Professional & scientific | 1974 |
| Cleenol in the Community CIC | Administrative & support | 2024 |
| Clelford Essex Associates Limited | Professional & scientific | 2005 |
| Clerpublica Ltd | Professional & scientific | 2026 |
| Clews Architects Ltd | Professional & scientific | 1994 |
| Click on Logistics Limited | Professional & scientific | 2000 |
| Clientface Limited | Professional & scientific | 2014 |
| Clifford Harris Ltd | Construction | 2013 |
| Clifton Dwellings Limited | Real estate | 2012 |
| Clifton Group Limited | Real estate | 2015 |
| Climatemp Solutions Limited | Professional & scientific | 2020 |
| Clinicall: Physio and Diagnostics Ltd | Health & social care | 2024 |
| Clipboard London Limited | Other services | 2018 |
| Clive Nichols Photography Limited | Professional & scientific | 2012 |
| Clive Reeves Ltd | Construction | 2012 |
| CLO Medical Ltd. | Health & social care | 2010 |
| Cloud 9 IP Limited | Information & communication | 2014 |
| Cloud Copy Limited | Arts & recreation | 2020 |
| Cloud HR Solutions Ltd | Administrative & support | 2023 |
| Cloud Sustain Ltd | Information & communication | 2023 |
| CLOUD9 Telecommunications Limited | Information & communication | 2021 |
| Cloudsrus Ltd. | Information & communication | 2014 |
| CM Creative Ltd | Wholesale & retail | 2021 |
| CM Management Limited | Arts & recreation | 2017 |
| Cmgl (1) Limited | Professional & scientific | 2001 |
| CMS Consolidated Holdings Ltd | Financial services | 2024 |
| CMS Wealth Holdings Ltd | Financial services | 2024 |
| CN Glass Ltd | Manufacturing | 1999 |
| Coach House Offices Ltd | Construction | 2022 |
| Coach House Projects Ltd | Construction | 2018 |
| Coacta Ltd | Arts & recreation | 2025 |
| Coastal Erosion and Flood Solutions Limited | Manufacturing | 2022 |
| Coatlectibles Ltd | Wholesale & retail | 2023 |
| COB Barn Consulting Ltd | Professional & scientific | 2016 |
| Cobu Illustration Ltd | Arts & recreation | 2019 |
| Coco Capital Limited | Real estate | 2015 |
| Coco Dotour Limited | Real estate | 2020 |
| Cocoapod (Oxford) Limited | Manufacturing | 2021 |
| Cocode Ltd | Information & communication | 2013 |
| Codeanddreams Ltd | Transport & logistics | 2018 |
| Codewell Limited | Information & communication | 2025 |
| Coffee & Corner Limited | Hospitality | 2025 |
| Coffee Engineering Co Ltd | Hospitality | 2024 |
| Coffee Import Axis Ltd | Wholesale & retail | 2025 |
| Coffeehouse Investments Limited | Extraterritorial | 2024 |
| Cohane Arts Limited | Wholesale & retail | 2023 |
| Cohesia Connect Ltd | Professional & scientific | 2022 |
| Cohesionix Ltd | Information & communication | 2024 |
| Cold Coffee Pictures Limited | Information & communication | 2019 |
| Coldharbour Farming Limited | Construction | 2012 |
| Colegrave Seeds Limited | Extraterritorial | 2001 |
| Coles Transport Limited | Transport & logistics | 2005 |
| Colin Woodward Agronomy Limited | Agriculture & fishing | 2022 |
| Collaborative Equity LLP | | 2013 |
| Collectaroo Limited | Extraterritorial | 2019 |
| Colleen Morris Limited | Professional & scientific | 2013 |
| College Fields (Aynho) Management Company Limited | Real estate | 2001 |
| Colourwood Ltd | Manufacturing | 2021 |
| Colwells Services Ltd | Manufacturing | 2020 |
| Come What MAY Films Ltd | Arts & recreation | 2022 |
| Comeonvilla! Ltd | Administrative & support | 2024 |
| Comflex Ltd | Real estate | 2023 |
| Comfort Cleaning Experts Ltd | Administrative & support | 2025 |
| Comglobus Ltd | Construction | 2020 |
| Commercial Developments (Shutford) Limited | Construction | 2016 |
| Commercial Developments (Southam) Ltd | Construction | 2016 |
| Community T'Ai CHI Chih CIC | Health & social care | 2025 |
| Complete Environment Group Limited | Administrative & support | 2025 |
| Complete Environment Ltd | Administrative & support | 2006 |
| Composit Ultra Ltd | Wholesale & retail | 2025 |
| Compton Court 2003 Limited | Households | 2003 |
| Compton Green Limited | Financial services | 2024 |
| Compton Therapies Limited | Other services | 2024 |
| Computing Dynamics Limited | Information & communication | 1994 |
| Concentric Watches Ltd | Manufacturing | 2018 |
| Concorde Security Limited | Administrative & support | 2016 |
| Confluent Marketing Limited | Administrative & support | 2018 |
| Connect Everything Aerospace Limited | Manufacturing | 2020 |
| Connect Everything Ltd | Information & communication | 2010 |
| Connect Medical Resources Limited | Administrative & support | 2005 |
| Connecting Education Ltd | Education | 2016 |
| Connectors & Switchgear Limited | Manufacturing | 1970 |
| Considered Connectivity Ltd | Information & communication | 2024 |
| Construction Fastener Techniques Limited | Extraterritorial | 1985 |
| Contact Light Innovation Ltd | Administrative & support | 2025 |
| Contact Sales Limited | Information & communication | 1997 |
| Contact Web Ltd | Administrative & support | 2023 |
| Containanstor Ltd | Real estate | 2020 |
| Continuity AI Ltd | Information & communication | 2026 |
| Contract HRM Limited | Administrative & support | 2010 |