| Cleaning & Services Ltd | Administrative & support | 2019 |
| Cleaning and Gardening Ltd | Administrative & support | 2021 |
| Cleaning Services by Elvira Limited | Administrative & support | 2019 |
| Cleaning Wizards Limited | Administrative & support | 2006 |
| Cleaningbyana Ltd | Administrative & support | 2026 |
| Cleanovationsuk Ltd | Administrative & support | 2024 |
| Cleanrite Limited | Administrative & support | 2024 |
| Cleanswwep Ltd | Administrative & support | 2025 |
| Cleanyx Limited | Administrative & support | 2026 |
| Clear Advice Mortgages Ltd | Financial services | 2025 |
| Clear Concepts IT Limited | Information & communication | 2014 |
| Clear Direction Human Resources Ltd | Professional & scientific | 2018 |
| Clear Glass Limited | Administrative & support | 2013 |
| Clear Glass Services Ltd | Construction | 2025 |
| Clear PLC | Transport & logistics | 2002 |
| Clear Reflection Cleaning Ltd | Administrative & support | 2023 |
| Clear Space Homes Limited | Construction | 2017 |
| Clear Space Marketing Limited | Professional & scientific | 2009 |
| Clear Utility Ltd | Administrative & support | 2023 |
| Clear Utility Solutions Ltd | Administrative & support | 2018 |
| Clear Vertical Limited | Information & communication | 2012 |
| Clear Vertical Ventures Limited | Professional & scientific | 2023 |
| Clear Watt Solutions Ltd | Construction | 2025 |
| Clearc Ltd | Administrative & support | 2022 |
| Clearline Commerce Limited | Wholesale & retail | 2025 |
| Clearpath Insights Ltd | Professional & scientific | 2025 |
| Clearpath Mental Health Ltd | Health & social care | 2025 |
| Clearspace Creative Limited | Professional & scientific | 2025 |
| Clearview Community Living C.I.C. | Real estate | 2025 |
| Clearview Ventures Limited | Professional & scientific | 2008 |
| Cleft Stick Limited | Information & communication | 2022 |
| Clement CT (F14) Limited | Real estate | 2023 |
| Clements Finance Limited | Financial services | 2008 |
| Clemerson and Sons Limited | Real estate | 1961 |
| Clemspat Ltd | Health & social care | 2021 |
| Clever at Software Limited | Information & communication | 2018 |
| Clever Cover Ltd | Administrative & support | 2016 |
| Clew Bay Consulting Limited | Extraterritorial | 2023 |
| Click Antiques Limited | Wholesale & retail | 2020 |
| Click Distribution (UK) Limited | Wholesale & retail | 2008 |
| Click Electrical Contractors Ltd | Construction | 2011 |
| Click&Deliver UK Ltd | Wholesale & retail | 2016 |
| Clickers Resources Ltd | Construction | 2024 |
| Clickin Solution Limited | Hospitality | 2014 |
| Clicklink Logistics Limited | Transport & logistics | 2016 |
| Clicks and Mortar Marketing Group Ltd | Wholesale & retail | 2015 |
| Clict Import & Distribution Limited | Wholesale & retail | 2011 |
| Clifford Smith Residents Management Company Limited | Real estate | 2024 |
| Clifford Towers (Accountants) Limited | Professional & scientific | 2002 |
| Clifford's Meats Ltd | Wholesale & retail | 2025 |
| Clifton Residents Management Company Limited | Real estate | 2021 |
| Cliftonville Court (2000) Limited | Households | 1999 |
| Cliftonville Dental Ltd | Health & social care | 2007 |
| Clikkasoftware Ltd | Information & communication | 2025 |
| Climacare Group Ltd | Manufacturing | 2016 |
| Climarsal Trustee Limited | Financial services | 1989 |
| Climbing High Nurseries Limited | Health & social care | 2003 |
| Climetech Ltd | Energy | 2025 |
| Climr Limited | Professional & scientific | 2010 |
| Clincoln UK Limited | Transport & logistics | 2025 |
| Clinfoss LLP | | 2022 |
| Clinic Services Limited | Administrative & support | 2020 |
| Clinical Cleaning Services Ltd | Administrative & support | 2024 |
| Clinical Decision Support Solutions Ltd | Information & communication | 2023 |
| Clinical Diagnostic Imaging Partnership Limited | Health & social care | 2012 |
| Clinical Pharm Ltd | Health & social care | 2022 |
| Clinical Training Limited | Public administration | 2011 |
| Clintreq Consultancy Ltd | Professional & scientific | 2015 |
| Clippers in the ASH Ltd | Other services | 2026 |
| Clive Capital Ltd | Households | 2019 |
| CLJ Engineering Ltd | Manufacturing | 2014 |
| CLL & Co Promotions Limited | Arts & recreation | 2010 |
| CLL Property Limited | Real estate | 2019 |
| CLM Building Services Limited | Construction | 2008 |
| Clma Investments Ltd | Financial services | 2021 |
| Cloakpoint Cybersecurity Limited | Information & communication | 2025 |
| Clock House Pizza Ltd | Hospitality | 2022 |
| Clohane Ltd | Real estate | 2022 |
| Clos Fine Wine Ltd | Wholesale & retail | 2023 |
| Closet Clothing Co Limited | Wholesale & retail | 1996 |
| Closet London Ltd | Wholesale & retail | 2010 |
| Cloud Farm Limited | Administrative & support | 2015 |
| Cloud Hub 360 Ltd | Information & communication | 2015 |
| Cloud Markers Ltd | Wholesale & retail | 2025 |
| Cloud Nine Holidays Limited | Transport & logistics | 2004 |
| Cloud Nine Platinum Ltd | Information & communication | 2010 |
| Cloud Possibilities Limited | Financial services | 2015 |
| Cloud Scale Solutions Ltd | Information & communication | 2025 |
| Cloud Select Ltd | Information & communication | 2023 |
| CLOUD9 People Ltd | Professional & scientific | 2015 |
| Cloudcore IT Solutions Ltd | Information & communication | 2025 |
| Clouds Enterprise Limited | Wholesale & retail | 2021 |
| Cloudtopia Ltd | Information & communication | 2015 |
| Clover Properties Limited | Real estate | 2023 |
| Cloverlea Petcare Ltd | Professional & scientific | 2015 |
| CLR Projects Limited | Real estate | 2006 |
| Club Bagel Ltd | Wholesale & retail | 2025 |
| Club Bensons Ltd | Hospitality | 2025 |
| Club Sports Snooker Limited | Administrative & support | 2021 |
| Clubglobalvip Limited | Administrative & support | 2025 |