| Cannons Construction Ltd | Construction | 2021 |
| Canoe and Kayak Tours Ltd | Arts & recreation | 2012 |
| Cantab Rock Ltd | Administrative & support | 2020 |
| Canvas Sky Limited | Information & communication | 1992 |
| Capital & Commitment Limited | Administrative & support | 1999 |
| Capital Finance Partners Limited | Financial services | 1998 |
| Capital LAB Ventures (Israel Tech I) LLP | | 2021 |
| Capital LAB Ventures (Smart Cities I) LLP | | 2021 |
| Capital LAB Ventures (UK Tech I) LLP | | 2021 |
| Capital LAB Ventures Investments LLP | | 2021 |
| Capital Valley Plastics Limited | Manufacturing | 1987 |
| Caps Training Limited | Education | 2022 |
| Capture Logistics Ltd | Transport & logistics | 2022 |
| Captus Limited | Professional & scientific | 2009 |
| Capulet Capital Management Limited | Financial services | 2022 |
| Car O Baar Ltd | Wholesale & retail | 2018 |
| Caradon Developments Ltd | Real estate | 2009 |
| Carat Creatives Ltd | Administrative & support | 2024 |
| Carbon Neutral Britain Ltd | Wholesale & retail | 2020 |
| Cardiac Locksmiths Limited | Wholesale & retail | 2012 |
| Cardzello Ltd | Professional & scientific | 2024 |
| Care by Volvo Car UK Limited | Wholesale & retail | 2018 |
| CARE999 Ltd | Administrative & support | 2017 |
| Caresphere LLC Ltd | Information & communication | 2025 |
| Cargill Statistical Consultancy Ltd | Education | 2012 |
| Cargonation United Kingdom Ltd | Transport & logistics | 2014 |
| Caribbean Wave Takeaway LLP | | 2021 |
| Carillion Communications Limited | Information & communication | 1993 |
| Carillion Communications Management Services Limited | Administrative & support | 2018 |
| Carisma Media Ltd | Professional & scientific | 2024 |
| Carmine Development Limited | Construction | 2020 |
| Carn Towan Limited | Real estate | 2022 |
| Carnexions Motor Company Ltd | Wholesale & retail | 2011 |
| Carolgamit Care Services Limited | Health & social care | 2016 |
| Carolina Trade Limited | Wholesale & retail | 2023 |
| Caromar Services Ltd | Administrative & support | 2024 |
| Carous Limited | Information & communication | 2025 |
| Carpentry by TIM Ltd | Manufacturing | 2021 |
| Carpet Homes Limited | Wholesale & retail | 1996 |
| Carrot Personal Training Limited Limited | Arts & recreation | 2014 |
| Cartco Limited | Construction | 2026 |
| Carterz Events Ltd | Arts & recreation | 2026 |
| Carz for Sale Limited | Wholesale & retail | 2021 |
| CAS Somersby Partnership LLP | | 2023 |
| Casa Fresco Cleaning Services Ltd | Households | 2015 |
| Casa MIA Limited | Real estate | 2015 |
| Case Topco Limited | Financial services | 2014 |
| Casemaker Packing Services Limited | Transport & logistics | 1990 |
| Caslas Trading Co Ltd | Financial services | 2024 |
| Cassini Publishing Limited | Information & communication | 2005 |
| Casstrom Limited | Wholesale & retail | 2006 |
| Cast Your Heritage Limited | Arts & recreation | 2023 |
| Castelvecchio Ltd | Professional & scientific | 2025 |
| Castle Building Products Limited | Professional & scientific | 1972 |
| Castle Cement (Chatburn) Limited | Professional & scientific | 1892 |
| Castle Cement (Clyde) Limited | Professional & scientific | 1891 |
| Castle Cement (Ketton) Limited | Financial services | 1928 |
| Castle Cement (Padeswood) Limited | Professional & scientific | 1975 |
| Castle Cement (Pitstone) Limited | Professional & scientific | 1975 |
| Castle Cement (Ribblesdale) Limited | Financial services | 1935 |
| Castle Cement Limited | Manufacturing | 1987 |
| Castle Clinic Limited | Health & social care | 2012 |
| Castle Court (Maidenhead) Residents Association Limited | Real estate | 1969 |
| Castle Lime Limited | Professional & scientific | 1964 |
| Castle Pension Scheme Trustees Limited | Professional & scientific | 2011 |
| Castle River Estates Limited | Real estate | 2025 |
| Cataleia Company Ltd | Other services | 2024 |
| Catalyst PWR Limited | Professional & scientific | 2015 |
| Catch ME IF YOU Cancer Ltd | Information & communication | 2021 |
| Categorycentric Ltd | Professional & scientific | 2013 |
| Catherine Neal Ltd | Professional & scientific | 2022 |
| Catts Solutions Ltd | Professional & scientific | 2000 |
| Cavanmorgan Ltd | Information & communication | 2022 |
| Cavendish Close Freehold (Taplow) Limited | Extraterritorial | 2008 |
| Cavendish Close Management Company (Taplow) Limited | Households | 1975 |
| Caverley Lightfoot Limited | Professional & scientific | 2018 |
| Caverncharm Limited | Financial services | 1994 |
| CAW Ventures Ltd | Hospitality | 2016 |
| Cazz & ME Ltd | Wholesale & retail | 2020 |
| CBR Management Services Ltd | Real estate | 2008 |
| CC Cleaners Ltd | Administrative & support | 2010 |
| CC Inventories Ltd | Real estate | 2024 |
| CC Window Cleaners Ltd | Administrative & support | 2010 |
| CCF Investments Limited | Real estate | 2020 |
| CCF Properties LLP | | 2016 |
| Ccjm Services Ltd | Information & communication | 2016 |
| CCR (Body Repairs) Limited | Wholesale & retail | 2014 |
| Ccwas Ltd | Transport & logistics | 2025 |
| Cedar Drive Management Limited | Households | 2004 |
| Cedars IRM Consulting Ltd | Real estate | 2011 |
| Ceera Ltd | Other services | 2011 |
| Celaris London Ltd | Wholesale & retail | 2023 |
| Celeus Ltd | Information & communication | 2019 |
| Centencia Limited | Professional & scientific | 2001 |
| Certic Certification Services | Professional & scientific | 2008 |
| Certiccs | Professional & scientific | 2009 |
| Certified Protection Limited | Financial services | 2019 |
| Cezary Perfect Building Project Ltd | Construction | 2018 |
| CF Advisory Services Limited | Financial services | 1998 |
| CFP Lottery and Raffles Limited | Other services | 1991 |