| Casa Puro Limited | Wholesale & retail | 2015 |
| Casa Space Technologies Limited | Manufacturing | 2024 |
| Casa Staffing Limited | Administrative & support | 2024 |
| Casa Ventures Limited | Administrative & support | 2008 |
| Casa-Tessuti Limited | Professional & scientific | 2013 |
| Casabel Holdings Limited | Real estate | 2016 |
| Casablanca Cleaning Ltd | Administrative & support | 2024 |
| Casablanca R Ltd | Hospitality | 2023 |
| Casacity Ltd | Real estate | 2023 |
| Casado Family Group Ltd | Hospitality | 2024 |
| Casals D.P (Management) Limited | Real estate | 2019 |
| Casami Property Group Limited | Real estate | 2026 |
| CASANAPOLI1926 Ltd | Hospitality | 2023 |
| Casatapas Limited | Hospitality | 2026 |
| Casaweb Ltd | Information & communication | 2025 |
| Casca Digital Ltd | Information & communication | 2022 |
| Cascade Commercial Finance Ltd | Administrative & support | 2012 |
| Cascade Hollow Support Network Ltd | Extraterritorial | 2026 |
| Cascade Infrastructure Holdings Limited | Financial services | 2025 |
| Cascade Infrastructure Limited | Construction | 2025 |
| Cascade North Limited | Financial services | 2025 |
| Cascade Ridge Business Advisors Ltd | Extraterritorial | 2026 |
| Cascadia Records Ltd | Wholesale & retail | 2025 |
| Cascelloid Limited | Extraterritorial | 2003 |
| Cascent Developments Limited | Real estate | 2024 |
| Case & Company Limited | Professional & scientific | 2014 |
| Case & Sons Limited | Wholesale & retail | 2016 |
| Case Building Services Limited | Construction | 2020 |
| Case Pro UK Limited | Information & communication | 2017 |
| Casekirk Ltd | Other services | 2012 |
| Caseman Holdings Ltd | Financial services | 2026 |
| Casesmarter Ltd | Information & communication | 2026 |
| Casey Manchester Limited | Construction | 2007 |
| Casey Plastering Services Ltd | Construction | 2025 |
| Casey Pozarowszczyk Ltd | Real estate | 2026 |
| Casey Roberts Hair & Beauty Ltd | Other services | 2022 |
| Casey Williams Ltd | Other services | 2018 |
| Casey's Corner Limited | Hospitality | 2023 |
| Casg Limited | Real estate | 2024 |
| Cash Cortex Competitions Ltd | Arts & recreation | 2025 |
| Cash for Cars NW Ltd | Wholesale & retail | 2026 |
| Cash Management Systems Limited | Professional & scientific | 1995 |
| Cash ME UP Ltd | Professional & scientific | 2026 |
| Cash Town Ltd | Wholesale & retail | 2025 |
| Cashier General Trading Ltd | Wholesale & retail | 2025 |
| Cashless Parking Limited | Information & communication | 2024 |
| Cashmore Estates Ltd. | Real estate | 2022 |
| Cashopper Limited | Wholesale & retail | 2012 |
| Casi.Kasi Limited | Financial services | 2018 |
| Casinal Limited | Professional & scientific | 2003 |
| Casio Property Limited | Construction | 2025 |
| Casius AI Ltd | Information & communication | 2025 |
| Casj Engineering Limited | Administrative & support | 2014 |
| Caskie E&C Ltd | Real estate | 2021 |
| Caslek International Limited | Wholesale & retail | 2024 |
| Caspar CUT Productions Ltd | Information & communication | 2025 |
| Caspar Hospitality Limited | Hospitality | 2022 |
| Casper Flow Ltd | Information & communication | 2025 |
| Casper Sewell Ltd | Wholesale & retail | 2025 |
| Caspertron Ltd | Hospitality | 2025 |
| Caspian Assured Holdings Limited | Financial services | 2024 |
| Caspian Assured Ltd | Financial services | 2009 |
| Caspian Pegasus Ltd | Extraterritorial | 2017 |
| Caspian Road Limited | Real estate | 2012 |
| Cass Properties Limited | Real estate | 2024 |
| Cassatt Limited | Manufacturing | 2025 |
| Cassellsguide Limited | Arts & recreation | 2014 |
| Casserly Investments Ltd | Real estate | 2017 |
| Casserly Properties Ltd | Real estate | 2023 |
| Casserly Property Management Ltd | Real estate | 2006 |
| Cassidy Maxwell Limited | Wholesale & retail | 2021 |
| Cassidy's MOT Limited | Water & waste | 2004 |
| Cassie Lomas Make UP Academy Ltd | Other services | 2010 |
| Cassini Asset Management Limited | Extraterritorial | 2011 |
| Cassiobury Court Rehabilitation Ltd | Health & social care | 2026 |
| Cassius Media Ltd | Professional & scientific | 2025 |
| Cassonx Limited | Professional & scientific | 2016 |
| Cast Group Holdings Ltd | Financial services | 2025 |
| Cast UK Limited | Administrative & support | 2005 |
| Castbless Estates Holdco Limited | Financial services | 2025 |
| Castbless Limited | Real estate | 2019 |
| Castel Food Company Ltd | Wholesale & retail | 2017 |
| Castellarius Ltd | Financial services | 2024 |
| Casti Capital Ltd | Wholesale & retail | 2020 |
| Casting Calls UK Ltd | Administrative & support | 2024 |
| Castle Beauty Limited | Other services | 2019 |
| Castle Brook Stables Ltd | Administrative & support | 2015 |
| Castle Care Homes Ltd | Health & social care | 2019 |
| Castle Hall Properties LLP | | 2009 |
| Castle HEY Management Co. Limited | Households | 2005 |
| Castle Hill Dental Practice Limited | Health & social care | 2010 |
| Castle Hill Estates Limited | Real estate | 2004 |
| Castle House (Holdings) Ltd | Financial services | 2025 |
| Castle Irwell Management Company Limited | Households | 2021 |
| Castle Metals UK Limited | Wholesale & retail | 2002 |
| Castle Mountain Ltd | Real estate | 2024 |
| Castle Rich (UK) Limited | Real estate | 2019 |
| Castle SG Ltd | Hospitality | 2023 |
| Castle Stede Limited | Administrative & support | 2018 |
| Castle Training & Consultancy Limited | Professional & scientific | 2021 |