| Carter Promotions Limited | Administrative & support | 2023 |
| Carter Robertson Developments Limited | Real estate | 2023 |
| Carter Software Development Limited | Information & communication | 2011 |
| Cartesian Analysis Ltd | Professional & scientific | 2014 |
| Carthy Skilling Electrical Ltd | Construction | 2013 |
| Cartwright Pond Limited | Construction | 2007 |
| Carvell Coding Limited | Health & social care | 2016 |
| Carwalader Ltd | Hospitality | 2020 |
| Carwise Limited | Wholesale & retail | 1999 |
| CAS Environmental Services Ltd | Agriculture & fishing | 2010 |
| CAS Holdings (NW) Limited | Real estate | 2019 |
| Casa Delivery Limited | Wholesale & retail | 2020 |
| Casa Emargaux Limited | Hospitality | 2024 |
| Casa Estates NW Ltd | Real estate | 2025 |
| Casa Faia Limited | Professional & scientific | 2024 |
| Casa Italia (UK) Ltd | Hospitality | 2008 |
| Casa Italian Restaurants Ltd | Real estate | 2014 |
| Casa Romaneasca 1 Ltd | Wholesale & retail | 2020 |
| Casa Romaneasca Ltd | Wholesale & retail | 2017 |
| Casa Roni Ltd | Hospitality | 2025 |
| Casa XL Ltd | Real estate | 2020 |
| Casara Limited | Real estate | 2019 |
| Casartelli Buildings Limited | Hospitality | 1991 |
| Casbah Coffee Club Limited | Administrative & support | 2010 |
| Cascade Capital Asset Management Ltd. | Administrative & support | 2019 |
| Cascade LA Ltd | Financial services | 2025 |
| Case Clinical Services Ltd | Health & social care | 2014 |
| Case Investments Ltd | Financial services | 2024 |
| Cash Advance Solutions Ltd | Financial services | 2025 |
| Cash Hunter Ltd | Hospitality | 2022 |
| Cashen Ltd | Financial services | 2025 |
| Cashflow Finance for Business UK Limited | Financial services | 2020 |
| Cashflow UK Limited | Financial services | 2000 |
| Cashtec Ltd | Wholesale & retail | 2006 |
| Casino Square Limited | Real estate | 2014 |
| Casita Living Limited | Real estate | 2017 |
| Casita Place Limited | Real estate | 2016 |
| Caspian Bridge International Ltd | Wholesale & retail | 2026 |
| Caspian Management UK Limited | Real estate | 2010 |
| Caspian NW Limited | Information & communication | 2022 |
| Cass Logistics & Recovery Limited | Transport & logistics | 2025 |
| Cassacreative Ltd | Hospitality | 2026 |
| Cassell Moore Law Limited | Professional & scientific | 2014 |
| Cassette Ltd | Extraterritorial | 2022 |
| Cassidy Offshore Ltd | Energy | 2025 |
| Cassidy Systems Limited | Manufacturing | 2021 |
| Cassie Cassandra Ltd | Information & communication | 2020 |
| Cassie Ltd | Hospitality | 2013 |
| Cassietoo Ltd | Hospitality | 2021 |
| Cassir & Co Ltd | | 1956 |
| Cast Civils & Groundworks Ltd | Construction | 2019 |
| Cast PP Limited | Other services | 2016 |
| Castan Trading Limited | Professional & scientific | 2019 |
| Castaway Homes Limited | Real estate | 2020 |
| Castell-On Ltd | Real estate | 2024 |
| Castle & Harrington Properties Limited | Professional & scientific | 2020 |
| Castle Accountant Services Ltd | Professional & scientific | 2017 |
| Castle Co NW Limited | Other services | 2017 |
| Castle Coco Ltd Ltd | Hospitality | 2024 |
| Castle EHS Consultants Ltd | Professional & scientific | 2017 |
| Castle Estates (Liverpool) Limited | Real estate | 2012 |
| Castle INT. Ltd | Professional & scientific | 2024 |
| Castle Keep Management Company Limited | Households | 1984 |
| Castle Marketing Co. Ltd | Administrative & support | 2023 |
| Castle Motor Engineers Ltd | Wholesale & retail | 2011 |
| Castle Peak Health Limited | Health & social care | 2026 |
| Castle Street Cocktail Company Limited | Hospitality | 2023 |
| Castle Street Entertainments Ltd | Hospitality | 2024 |
| Castle Suites Limited | Real estate | 2016 |
| Castle Travel Limited | Administrative & support | 2018 |
| Castle Venture Capital Limited | Professional & scientific | 2009 |
| Castle Walk Management Company Limited | Real estate | 2017 |
| Castle Wealth International Ltd | Financial services | 2022 |
| Castle Wealth Land Limited | Real estate | 2023 |
| Castle Wealth Property Partners Limited | Real estate | 2023 |
| Castlecoding Ltd | Professional & scientific | 2024 |
| Castlemoat Group Limited | Construction | 2018 |
| Castlemount Developments Limited | Construction | 1987 |
| Castlerigg Estates Limited | Real estate | 2002 |
| Castles Equine Ltd | Agriculture & fishing | 2023 |
| Castleton Cottage Limited | Hospitality | 2021 |
| Castrol (U.K.) Limited | Administrative & support | 1988 |
| Castros Convenience Store Limited | Wholesale & retail | 2022 |
| Casus PAX CIC | Health & social care | 2022 |
| Cat Deacon Transport Limited | Transport & logistics | 2014 |
| Cat Family Investment Company | Real estate | 2025 |
| Cat Film Service & Production Ltd | Information & communication | 2021 |
| Cat's EYE Property Ltd | Construction | 2026 |
| Cata MAR Trans Ltd | Transport & logistics | 2017 |
| Cataclean Global Limited | Wholesale & retail | 2000 |
| Cataclean International Ltd | Wholesale & retail | 2013 |
| Catalan Wines Ltd | Wholesale & retail | 2014 |
| Cataland Ltd | Extraterritorial | 2014 |
| Catalyst BNI Ltd | Other services | 2000 |
| Catalyst Dance & Drama Group Limited | Arts & recreation | 1994 |
| Catalyst Energy Ltd | Construction | 2013 |
| Catalyst Nation Ltd | Hospitality | 2025 |
| Catarata Limited | Real estate | 2023 |
| Catarina Brazilian Sweets Ltd | Hospitality | 2025 |
| Catbev Baltic Ltd | Hospitality | 2024 |